Although hydrogels have been widely investigated for their use in materials science, nanotechnolo... more Although hydrogels have been widely investigated for their use in materials science, nanotechnology, and novel pharmaceuticals, mechanistic details explaining their water-absorbent features are not well understood. We performed an all-atom molecular dynamics study of the structural transformation of chitosan nanohydrogels due to water absorption. We analyzed the conformation of dry, nanoscaled chitosan, the structural modifications that emerge during the process of water inclusion, and the dynamics of this biopolymer in the presence of nature's solvent. Two sets of nanoscaled, single-chained chitosan models were simulated: one to study the swelling dependence upon the degree of self-crosslinking and other to observe the response with respect to the degree of protonation. We verified that nanohydrogels keep their ability to absorb water and grow, regardless of their degree of cross-linking. Noteworthy, we found that the swelling behavior of nanoscaled chitosan is pH-dependent, and it is considerably more limited than that of larger scale hydrogels. Thus, our study suggests that properties of nanohydrogels are significantly different from those of larger hydrogels. These findings might be important in the design of novel controlled-release and targeted drug-delivery systems based on chitosan.
Employing the phase-space representation of second order ordinary differential equations we devel... more Employing the phase-space representation of second order ordinary differential equations we developed a method to find the eigenvalues and eigenfunctions of the 1dimensional time independent Schrödinger equation for quantum model systems. The method presented simplifies some approaches shown in textbooks, based on asymptotic analyses of the time-independent Schrödinger equation, and power series methods with recurrence relations. In addition, the method presented here facilitates the understanding of the relationship between the ordinary differential equations of the mathematical physics and the time independent Schrödinger equation of physical models as the harmonic oscillator, the rigid rotor, the Hydrogen atom, and the Morse oscillator.
A general closed-form expression for $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] of solutions ... more A general closed-form expression for $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] of solutions of a weak acid and a weak acid buffer, as well as their titration with a strong base, has been obtained and mathematically analyzed with the aid of computer algebra systems. This expression is used to evaluate, without the use of numerical approximations, the precision and accuracy of different approximations commonly employed in general chemistry and chemical analysis courses. The closed-form expression for $${{[\textrm{H}_{3}\textrm{O}^+]}}$$ [ H 3 O + ] of a buffer solution is used to obtain an analytical expression for the pH stability when a strong base is added. Finally, it is shown that the $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] expressions for all the systems under study can be obtained from a general closed-form expression in terms of an effective weak acid constant and an effective acid concentration. The formulas found in this work do not display numerical rounding err...
Closed-form algebraic expressions for the pH of ideal weak acid and weak acid buffer solutions (a... more Closed-form algebraic expressions for the pH of ideal weak acid and weak acid buffer solutions (and their titration with a strong base) were obtained and analyzed with the aid of computer algebra systems. These expressions are used to evaluate, without the use of numerical approximations, the precision and accuracy of different approximations commonly employed to calculate the pH. The closed-form expression for the pH of a buffer solution is used to obtain an analytical expression for the pH stability when a strong base is added. Finally, it is shown that the pH expressions for all the systems under study can be obtained from an unique closed-form expression in terms of an effective weak acid constant and an effective acid concentration.
We recently proposed a Quantum Optimal Control (QOC) method constrained to build pulses from anal... more We recently proposed a Quantum Optimal Control (QOC) method constrained to build pulses from analytical pulse shapes [R. D. Guerrero et al., J. Chem. Phys. 143(12), 124108 (2015)]. This approach was applied to control the dissociation channel yields of the diatomic molecule KH, considering three potential energy curves and one degree of freedom. In this work, we utilized this methodology to study the strong field control of the cis-trans photoisomerization of 11-cis retinal. This more complex system was modeled with a Hamiltonian comprising two potential energy surfaces and two degrees of freedom. The resulting optimal pulse, made of 6 linearly chirped pulses, was capable of controlling the population of the trans isomer on the ground electronic surface for nearly 200 fs. The simplicity of the pulse generated with our QOC approach offers two clear advantages: a direct analysis of the sequence of events occurring during the driven dynamics, and its reproducibility in the laboratory w...
Coherent control theory is applied to the control of Ne*(3s,(3)P2)+Ar((1)S0) collisions and compu... more Coherent control theory is applied to the control of Ne*(3s,(3)P2)+Ar((1)S0) collisions and computations are shown that display extensive control over these processes. Indeed we demonstrate that it is possible to essentially turn on and off the cross sections for both the Penning and associative ionization processes. This facility arises from the interference between matter waves induced by creating a linear superposition of the degenerate M={-2,-1,0,1,2} Zeeman sublevels of the Ne*(3s,(3)P2) target atom. The computations, conducted at collision energies in the 1-8 kcal/mole range, are based on combining, within the "rotating atom approximation," empirically derived and ab initio ionization widths.
We propose a methodology to design optimal pulses for achieving quantum optimal control on molecu... more We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function with genetic algorithms. As a first application of the methodology we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.
We investigate the classical mechanics of diatomic and symmetric top molecules in tilted fields. ... more We investigate the classical mechanics of diatomic and symmetric top molecules in tilted fields. These molecules exhibit regular, chaotic or mixed phase space depending on the tilt angle β, the energy E, and the relative intensity of the fields ω/∆ω. In the integrable collinear problem the projection of the angular momentum into the spatial z axis is a constant of motion, m, which allows us to explore the geometry of the phase space, and to use energy momentum diagrams to classify the motions of the rotor. For β = 0 the system is non-integrable showing mostly regular dynamics in the high-energy (free-rotor) and low-energy (pendular) limits; for energy near the tilted fields barrier the phase space is highly chaotic with degree of chaos increasing with β between 0 and π/2. Periodic orbits and bifurcation diagrams are obtained from symmetry lines and their iterations under the Poincaré map. These bifurcation diagrams are used to observe the changes in the basic structure of the phase space as β changes between collinear and perpendicular fields. Some quantum eigenstates are localized near stable or unstable periodic orbits showing tori quantization or scarring respectively. For asymmetric top molecules only the case of collinear fields is treated. In parallel fields m is a constant of the motion and it is possible to define an effective potential V m (θ, ψ). In an E-m diagram the equilibrium solutions of V m (θ, ψ) are curves that enclose regions of qualitatively different accessible θ-ψ configuration space. Interestingly these regions can be used to classify the quantum eigenstates. For plane rotors primitive semiclassical mechanics is used to calculate the rotational excitation caused by laser pulses. Depending on the pulse intensity and duration several methods are employed from the analytical sudden approximation to primitive semiclassical initial value representation (IVR) integrals. The calculated transition probabilities are in good agreement with the quantum probabilities considering the simplicity of the methods. In the case of plane rotors in electric fields we calculate energy spectra, orientation (cos ϕ), and alignment (cos 2 ϕ), using the Herman-Kluk propagator in terms of periodic coherent states. These results are in good agreement with the quantum analogues although the number of trajectories used is discouragingly large. For diatomic rotors in tilted fields, the HK propagator was used to calculate energy spectra with good agreement for high-energy and not very dense eigenspectra. Some steps are taken towards the development of HK-type propagator for rotational coherent states. BIOGRAPHICAL SKETCH Carlos Alberto Arango was born on September 6th, 1973, in the colonial city of Popayán Colombia. His family moved to the warmer city of Santiago de Cali in 1976 where he completed elementary and secondary education graduating from Colegio Americano in 1990. In the summer of 1991 he began college with major in Chemistry at Universidad del Valle in Cali, graduating in summer 1997 after finishing his thesis under the direction of Gustavo Sánchez. He continued studying in the same university obtaining a M.Sc. in chemistry in summer 2000, with thesis directed by professor Julio Arce. In summer 2000 he entered the Ph.D. program in
We apply the 'classic' semiclassical initial value representation (SC-IVR) approach to describe r... more We apply the 'classic' semiclassical initial value representation (SC-IVR) approach to describe rotational excitation of non-polar diatomic molecules by intense short non-resonant laser pulses. We also investigate the applicability of the quantum mechanical sudden approximation. It is found that the SC-IVR approach gives accurate rotational excitation probabilities in regimes where the sudden approximation fails. Primitive semiclassical wavefunction propagation is used to illustrate the phenomenon of angular focussing of rotation states by strong pulses.
International Journal of Bifurcation and Chaos, 2008
We study classical energy-momentum (E-m) diagrams for rotational motion of dipolar asymmetric top... more We study classical energy-momentum (E-m) diagrams for rotational motion of dipolar asymmetric top molecules in strong external fields. Static electric fields, nonresonant linearly polarized laser fields, and collinear combinations of the two are investigated. We treat specifically the molecules iodobenzene (a nearly prolate asymmetric top), pyridazine (nearly oblate asymmetric top), and iodopentafluorobenzene (intermediate case). The location of relative equilibria in the E-m plane and associated bifurcations are determined by straightforward calculation, with analytical results given where possible. In cases where analytical solutions cannot be obtained, we resort to numerical solutions, while keeping a geometrical picture of the nature of the solutions to the fore. The classification we obtain of the topology of classically allowed rotor configuration space regions in the E-m diagram is of potential use in characterization of energy eigenstates of the corresponding quantum mechani...
Coherent Control techniques are computationally applied to cold (1 mK < T < 1 K) and ultracold (T... more Coherent Control techniques are computationally applied to cold (1 mK < T < 1 K) and ultracold (T < 1 µK) Ne * (3s, 3 P2) + Ar(1 S0) collisions. We show that by using various initial superpositions of the Ne * (3s, 3 P2) M = {−2, −1, 0, 1, 2} Zeeman sub-levels it is possible to reduce the Penning Ionization (PI) and Associative Ionization (AI) cross sections by as much as four orders of magnitude. It is also possible to drastically change the ratio of these two processes. The results are based on combining, within the "Rotating Atom Approximation", empirical and ab-initio ionization-widths.
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, co... more Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous
We computationally demonstrate the one-photon phase control of retinal isomerization under condit... more We computationally demonstrate the one-photon phase control of retinal isomerization under conditions of low laser intensity. The calculations, utilizing the multiconfigurational time dependent Hartree method, include coupling between the two modes that are active in isomerization and the background molecular vibrational environment. Noting previously unsuccessful computations highlights the significance of this result.
A mathematical phase-space representation of the 1-dimensional Schrodinger equation is employed t... more A mathematical phase-space representation of the 1-dimensional Schrodinger equation is employed to obtain bound and resonance states of the rotationally excited H$_2$ molecule. The structure of the phase-space tangent field is analyzed and related to the behavior of the wave function in classically allowed and forbidden regions. In this phase-space representation, bound states behave like unstable orbits meanwhile resonance states behave similarly to asymptotically stable cycles. The lattice of quantum states of the energy-momentum diagram for H$_2$ is calculated allowing to have a global view of the energy as function of the quantum numbers. The arc length and winding number of the phase-space trajectories, as functions of the energy, are used to obtain the energy eigenvalues of bound and resonance states of H$_2$
Employing the phase-space representation of second order ordinary differential equations we devel... more Employing the phase-space representation of second order ordinary differential equations we developed a method to find the eigenvalues and eigenfunctions of the 1dimensional time independent Schrödinger equation for quantum model systems. The method presented simplifies some approaches shown in textbooks, based on asymptotic analyses of the time-independent Schrödinger equation, and power series methods with recurrence relations. In addition, the method presented here facilitates the understanding of the relationship between the ordinary differential equations of the mathematical physics and the time independent Schrödinger equation of physical models as the harmonic oscillator, the rigid rotor, the Hydrogen atom, and the Morse oscillator.
A system of two bilinearly coupled harmonic oscillators has been solved analytically by using the... more A system of two bilinearly coupled harmonic oscillators has been solved analytically by using the Born-Oppenheimer (BO) product wavefunction ansatz and the phasespace bound trajectory approach [J. S. Molano et al., Chem. Phys. Lett. 76(12), 138171 (2021)]. The bilinearly coupled oscillator system allows to obtain the analytical expression of the quantum system, facilitating comparison with the results of using the BO ansatz product. The analytical and BO wavefunctions are obtained as a product of parabolic cylinder functions. The arguments of the parabolic cylinder functions of the exact and the BO wavefunctions are related to the physical coordinates by linear transformations, represented by matrices G and G̃ respectively. A QU decomposition of the matrix G outputs an upper triangular matrix U that is closely related to the BO G̃ matrix. The effect of the BO non-adiabatic coupling is analyzed on the stability of the phase-space equations of motion. The eigenvalues and eigenfunction...
We proposed a methodology that allows to maximize the population transfer from a high vibrational... more We proposed a methodology that allows to maximize the population transfer from a high vibrational state of the a 3 Σ + triplet state to the vibrational ground state of the X 1 Σ + singlet state though the optimization of one pump and one dump laser pulses. The pump pulse is optimized using a fitness function, heuristically improved, that includes the effect of the spin-orbit coupling of the KRb [b-A]-scheme. The dump pulse is optimized to maximize the population transfer to the ground state. We performed a comparison with the case in which the pump and dump pulses are optimized to maximize the population transfer to the ground state employing a genetic algorithm with a single fitness function. The heuristic approach turned out to be 70% more efficient than a quantum optimal control optimization employing a single fitness function. The method proposed provides simple pulses that have an experimental realm.
Although hydrogels have been widely investigated for their use in materials science, nanotechnolo... more Although hydrogels have been widely investigated for their use in materials science, nanotechnology, and novel pharmaceuticals, mechanistic details explaining their water-absorbent features are not well understood. We performed an all-atom molecular dynamics study of the structural transformation of chitosan nanohydrogels due to water absorption. We analyzed the conformation of dry, nanoscaled chitosan, the structural modifications that emerge during the process of water inclusion, and the dynamics of this biopolymer in the presence of nature's solvent. Two sets of nanoscaled, single-chained chitosan models were simulated: one to study the swelling dependence upon the degree of self-crosslinking and other to observe the response with respect to the degree of protonation. We verified that nanohydrogels keep their ability to absorb water and grow, regardless of their degree of cross-linking. Noteworthy, we found that the swelling behavior of nanoscaled chitosan is pH-dependent, and it is considerably more limited than that of larger scale hydrogels. Thus, our study suggests that properties of nanohydrogels are significantly different from those of larger hydrogels. These findings might be important in the design of novel controlled-release and targeted drug-delivery systems based on chitosan.
Employing the phase-space representation of second order ordinary differential equations we devel... more Employing the phase-space representation of second order ordinary differential equations we developed a method to find the eigenvalues and eigenfunctions of the 1dimensional time independent Schrödinger equation for quantum model systems. The method presented simplifies some approaches shown in textbooks, based on asymptotic analyses of the time-independent Schrödinger equation, and power series methods with recurrence relations. In addition, the method presented here facilitates the understanding of the relationship between the ordinary differential equations of the mathematical physics and the time independent Schrödinger equation of physical models as the harmonic oscillator, the rigid rotor, the Hydrogen atom, and the Morse oscillator.
A general closed-form expression for $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] of solutions ... more A general closed-form expression for $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] of solutions of a weak acid and a weak acid buffer, as well as their titration with a strong base, has been obtained and mathematically analyzed with the aid of computer algebra systems. This expression is used to evaluate, without the use of numerical approximations, the precision and accuracy of different approximations commonly employed in general chemistry and chemical analysis courses. The closed-form expression for $${{[\textrm{H}_{3}\textrm{O}^+]}}$$ [ H 3 O + ] of a buffer solution is used to obtain an analytical expression for the pH stability when a strong base is added. Finally, it is shown that the $${[\textrm{H}_{3}\textrm{O}^+]}$$ [ H 3 O + ] expressions for all the systems under study can be obtained from a general closed-form expression in terms of an effective weak acid constant and an effective acid concentration. The formulas found in this work do not display numerical rounding err...
Closed-form algebraic expressions for the pH of ideal weak acid and weak acid buffer solutions (a... more Closed-form algebraic expressions for the pH of ideal weak acid and weak acid buffer solutions (and their titration with a strong base) were obtained and analyzed with the aid of computer algebra systems. These expressions are used to evaluate, without the use of numerical approximations, the precision and accuracy of different approximations commonly employed to calculate the pH. The closed-form expression for the pH of a buffer solution is used to obtain an analytical expression for the pH stability when a strong base is added. Finally, it is shown that the pH expressions for all the systems under study can be obtained from an unique closed-form expression in terms of an effective weak acid constant and an effective acid concentration.
We recently proposed a Quantum Optimal Control (QOC) method constrained to build pulses from anal... more We recently proposed a Quantum Optimal Control (QOC) method constrained to build pulses from analytical pulse shapes [R. D. Guerrero et al., J. Chem. Phys. 143(12), 124108 (2015)]. This approach was applied to control the dissociation channel yields of the diatomic molecule KH, considering three potential energy curves and one degree of freedom. In this work, we utilized this methodology to study the strong field control of the cis-trans photoisomerization of 11-cis retinal. This more complex system was modeled with a Hamiltonian comprising two potential energy surfaces and two degrees of freedom. The resulting optimal pulse, made of 6 linearly chirped pulses, was capable of controlling the population of the trans isomer on the ground electronic surface for nearly 200 fs. The simplicity of the pulse generated with our QOC approach offers two clear advantages: a direct analysis of the sequence of events occurring during the driven dynamics, and its reproducibility in the laboratory w...
Coherent control theory is applied to the control of Ne*(3s,(3)P2)+Ar((1)S0) collisions and compu... more Coherent control theory is applied to the control of Ne*(3s,(3)P2)+Ar((1)S0) collisions and computations are shown that display extensive control over these processes. Indeed we demonstrate that it is possible to essentially turn on and off the cross sections for both the Penning and associative ionization processes. This facility arises from the interference between matter waves induced by creating a linear superposition of the degenerate M={-2,-1,0,1,2} Zeeman sublevels of the Ne*(3s,(3)P2) target atom. The computations, conducted at collision energies in the 1-8 kcal/mole range, are based on combining, within the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;rotating atom approximation,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; empirically derived and ab initio ionization widths.
We propose a methodology to design optimal pulses for achieving quantum optimal control on molecu... more We propose a methodology to design optimal pulses for achieving quantum optimal control on molecular systems. Our approach constrains pulse shapes to linear combinations of a fixed number of experimentally relevant pulse functions. Quantum optimal control is obtained by maximizing a multi-target fitness function with genetic algorithms. As a first application of the methodology we generated an optimal pulse that successfully maximized the yield on a selected dissociation channel of a diatomic molecule. Our pulse is obtained as a linear combination of linearly chirped pulse functions. Data recorded along the evolution of the genetic algorithm contained important information regarding the interplay between radiative and diabatic processes. We performed a principal component analysis on these data to retrieve the most relevant processes along the optimal path. Our proposed methodology could be useful for performing quantum optimal control on more complex systems by employing a wider variety of pulse shape functions.
We investigate the classical mechanics of diatomic and symmetric top molecules in tilted fields. ... more We investigate the classical mechanics of diatomic and symmetric top molecules in tilted fields. These molecules exhibit regular, chaotic or mixed phase space depending on the tilt angle β, the energy E, and the relative intensity of the fields ω/∆ω. In the integrable collinear problem the projection of the angular momentum into the spatial z axis is a constant of motion, m, which allows us to explore the geometry of the phase space, and to use energy momentum diagrams to classify the motions of the rotor. For β = 0 the system is non-integrable showing mostly regular dynamics in the high-energy (free-rotor) and low-energy (pendular) limits; for energy near the tilted fields barrier the phase space is highly chaotic with degree of chaos increasing with β between 0 and π/2. Periodic orbits and bifurcation diagrams are obtained from symmetry lines and their iterations under the Poincaré map. These bifurcation diagrams are used to observe the changes in the basic structure of the phase space as β changes between collinear and perpendicular fields. Some quantum eigenstates are localized near stable or unstable periodic orbits showing tori quantization or scarring respectively. For asymmetric top molecules only the case of collinear fields is treated. In parallel fields m is a constant of the motion and it is possible to define an effective potential V m (θ, ψ). In an E-m diagram the equilibrium solutions of V m (θ, ψ) are curves that enclose regions of qualitatively different accessible θ-ψ configuration space. Interestingly these regions can be used to classify the quantum eigenstates. For plane rotors primitive semiclassical mechanics is used to calculate the rotational excitation caused by laser pulses. Depending on the pulse intensity and duration several methods are employed from the analytical sudden approximation to primitive semiclassical initial value representation (IVR) integrals. The calculated transition probabilities are in good agreement with the quantum probabilities considering the simplicity of the methods. In the case of plane rotors in electric fields we calculate energy spectra, orientation (cos ϕ), and alignment (cos 2 ϕ), using the Herman-Kluk propagator in terms of periodic coherent states. These results are in good agreement with the quantum analogues although the number of trajectories used is discouragingly large. For diatomic rotors in tilted fields, the HK propagator was used to calculate energy spectra with good agreement for high-energy and not very dense eigenspectra. Some steps are taken towards the development of HK-type propagator for rotational coherent states. BIOGRAPHICAL SKETCH Carlos Alberto Arango was born on September 6th, 1973, in the colonial city of Popayán Colombia. His family moved to the warmer city of Santiago de Cali in 1976 where he completed elementary and secondary education graduating from Colegio Americano in 1990. In the summer of 1991 he began college with major in Chemistry at Universidad del Valle in Cali, graduating in summer 1997 after finishing his thesis under the direction of Gustavo Sánchez. He continued studying in the same university obtaining a M.Sc. in chemistry in summer 2000, with thesis directed by professor Julio Arce. In summer 2000 he entered the Ph.D. program in
We apply the 'classic' semiclassical initial value representation (SC-IVR) approach to describe r... more We apply the 'classic' semiclassical initial value representation (SC-IVR) approach to describe rotational excitation of non-polar diatomic molecules by intense short non-resonant laser pulses. We also investigate the applicability of the quantum mechanical sudden approximation. It is found that the SC-IVR approach gives accurate rotational excitation probabilities in regimes where the sudden approximation fails. Primitive semiclassical wavefunction propagation is used to illustrate the phenomenon of angular focussing of rotation states by strong pulses.
International Journal of Bifurcation and Chaos, 2008
We study classical energy-momentum (E-m) diagrams for rotational motion of dipolar asymmetric top... more We study classical energy-momentum (E-m) diagrams for rotational motion of dipolar asymmetric top molecules in strong external fields. Static electric fields, nonresonant linearly polarized laser fields, and collinear combinations of the two are investigated. We treat specifically the molecules iodobenzene (a nearly prolate asymmetric top), pyridazine (nearly oblate asymmetric top), and iodopentafluorobenzene (intermediate case). The location of relative equilibria in the E-m plane and associated bifurcations are determined by straightforward calculation, with analytical results given where possible. In cases where analytical solutions cannot be obtained, we resort to numerical solutions, while keeping a geometrical picture of the nature of the solutions to the fore. The classification we obtain of the topology of classically allowed rotor configuration space regions in the E-m diagram is of potential use in characterization of energy eigenstates of the corresponding quantum mechani...
Coherent Control techniques are computationally applied to cold (1 mK < T < 1 K) and ultracold (T... more Coherent Control techniques are computationally applied to cold (1 mK < T < 1 K) and ultracold (T < 1 µK) Ne * (3s, 3 P2) + Ar(1 S0) collisions. We show that by using various initial superpositions of the Ne * (3s, 3 P2) M = {−2, −1, 0, 1, 2} Zeeman sub-levels it is possible to reduce the Penning Ionization (PI) and Associative Ionization (AI) cross sections by as much as four orders of magnitude. It is also possible to drastically change the ratio of these two processes. The results are based on combining, within the "Rotating Atom Approximation", empirical and ab-initio ionization-widths.
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, co... more Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous
We computationally demonstrate the one-photon phase control of retinal isomerization under condit... more We computationally demonstrate the one-photon phase control of retinal isomerization under conditions of low laser intensity. The calculations, utilizing the multiconfigurational time dependent Hartree method, include coupling between the two modes that are active in isomerization and the background molecular vibrational environment. Noting previously unsuccessful computations highlights the significance of this result.
A mathematical phase-space representation of the 1-dimensional Schrodinger equation is employed t... more A mathematical phase-space representation of the 1-dimensional Schrodinger equation is employed to obtain bound and resonance states of the rotationally excited H$_2$ molecule. The structure of the phase-space tangent field is analyzed and related to the behavior of the wave function in classically allowed and forbidden regions. In this phase-space representation, bound states behave like unstable orbits meanwhile resonance states behave similarly to asymptotically stable cycles. The lattice of quantum states of the energy-momentum diagram for H$_2$ is calculated allowing to have a global view of the energy as function of the quantum numbers. The arc length and winding number of the phase-space trajectories, as functions of the energy, are used to obtain the energy eigenvalues of bound and resonance states of H$_2$
Employing the phase-space representation of second order ordinary differential equations we devel... more Employing the phase-space representation of second order ordinary differential equations we developed a method to find the eigenvalues and eigenfunctions of the 1dimensional time independent Schrödinger equation for quantum model systems. The method presented simplifies some approaches shown in textbooks, based on asymptotic analyses of the time-independent Schrödinger equation, and power series methods with recurrence relations. In addition, the method presented here facilitates the understanding of the relationship between the ordinary differential equations of the mathematical physics and the time independent Schrödinger equation of physical models as the harmonic oscillator, the rigid rotor, the Hydrogen atom, and the Morse oscillator.
A system of two bilinearly coupled harmonic oscillators has been solved analytically by using the... more A system of two bilinearly coupled harmonic oscillators has been solved analytically by using the Born-Oppenheimer (BO) product wavefunction ansatz and the phasespace bound trajectory approach [J. S. Molano et al., Chem. Phys. Lett. 76(12), 138171 (2021)]. The bilinearly coupled oscillator system allows to obtain the analytical expression of the quantum system, facilitating comparison with the results of using the BO ansatz product. The analytical and BO wavefunctions are obtained as a product of parabolic cylinder functions. The arguments of the parabolic cylinder functions of the exact and the BO wavefunctions are related to the physical coordinates by linear transformations, represented by matrices G and G̃ respectively. A QU decomposition of the matrix G outputs an upper triangular matrix U that is closely related to the BO G̃ matrix. The effect of the BO non-adiabatic coupling is analyzed on the stability of the phase-space equations of motion. The eigenvalues and eigenfunction...
We proposed a methodology that allows to maximize the population transfer from a high vibrational... more We proposed a methodology that allows to maximize the population transfer from a high vibrational state of the a 3 Σ + triplet state to the vibrational ground state of the X 1 Σ + singlet state though the optimization of one pump and one dump laser pulses. The pump pulse is optimized using a fitness function, heuristically improved, that includes the effect of the spin-orbit coupling of the KRb [b-A]-scheme. The dump pulse is optimized to maximize the population transfer to the ground state. We performed a comparison with the case in which the pump and dump pulses are optimized to maximize the population transfer to the ground state employing a genetic algorithm with a single fitness function. The heuristic approach turned out to be 70% more efficient than a quantum optimal control optimization employing a single fitness function. The method proposed provides simple pulses that have an experimental realm.
Uploads
Papers by Carlos Arango