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International Journal of Quantum Chemistry

Effects of the dipole moments behavior on a vibronic coupling model for the four‐wave mixing signal

Teresa Cusati, José Luis Paz, A. J. Hernández

Published Jan 1, 2004• 2 citations
Publisher

Abstract

Abstract In the present work, we have studied modifications in the transition and permanent dipole moments of states in a coupled basis (including vibronic coupling) due to variations in the transition dipole moment between the uncoupled states, m 12 , as a function of the parameter δ = $\tilde{\omega}$ 0 /ω 0 (relative aperture) of the potential‐energy curves of the states involved. Modifications in the slopes of the transition and permanent dipole moments of the coupled states and changes in the magnitude of maximal intensity of the four‐wave mixing (FWM) signal are observed due to variations in these parameters. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

DOI
10.1002/qua.20076

Related papers

Modifications in the Maximal Intensity of Four-Wave Mixing Signal under the Changes of Vibronic Coupling Conditions #

BioChem Press, José Luis Paz, Teresa Cusati +1 more

Motivation. The spectroscopic analysis of the behavior of the nonlinear signal response of systems including electronic levels is described by the coupling parameters of crossed harmonic potential curves. Method. Changes in the Four–Wave Mixing (FWM) signal intensity are originated by the modifications of the dipole moments in the new coupled basis due to variation of the parameters V0 (energetic difference between the minima), v (coupling parameter) and G (strength constant) corresponding to the crossed states involved. The permanent dipole moments of the states in the uncoupled basis have been included and the Rotating–Wave Approximation is neglected in order to observe the processes out of the resonance region. The calculation method is based in the Liouville–von Neumann formalism for the density matrix, where the Conventional Optical Bloch Equations are solved in Fourier space to obtain the density matrix elements associated with the Macroscopic Polarization responsible of the FWM signal. Results. Variation in the coupling parameters generates modifications in the dipole moments of the coupled states. These modifications induce changes in the intensity values of the FWM signal, including the nullity of the dipole moments producing the nullity of the nonlinear signal. Mathematical expressions are obtained to interpret these results. Conclusions. Changes in the characteristic coupling parameters induce modifications on the crossed potential curves, and consequently, on the nonlinear response and intensity.

•Jan 1, 2004•1 citation

Influence of changes in dipole moments of a system with intramolecular coupling on the four-wave mixing signal

Teresa Cusati, José Luis Paz

In this work we study the changes in the Four-Wave Mixing (FWM) signal with the modification of the permanent and transition dipolar moments of states in a coupled basis (under the inclusion of intramolecular coupling phenomenon), due to the changes in different parameters, such as coupling parameters v and Vo, strength constant Δ, and transition dipolar moment between the uncoupled states m12. Changes in the intensity and position of the resonances in the FWM signal spectra are observed with the variation in the parameters mentioned above.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Nov 18, 2003•0 citations

Modification in the relaxation times and strength constant of potential curves in four-wave mixing

Teresa Cusati, José Luis Paz, M. C. Salazar +1 more

In this work we have studied the changes in the Four-Wave Mixing (FWM) signal with the changes in the ratio between the longitudinal and transversal relation times T1/T2. Moreover, we have studied too the modifications in the FWM signal with the changes in the strength constant of the crossed harmonic potential curves that describe the two- levels system employed to this study. We have included the permanent dipolar moments of the states in the uncoupled basis. The rotating wave approximation is neglected to observe the process out of the resonance region. We observed changes in the shape, intensity and position in the resonances of the FWM signal spectra, with the changes in the ratio T1T2 and the strength constant (delta) .© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Aug 14, 2001•0 citations

Changes in Dipole Moments and Polarization of a Two-Level System with Intramolecular Coupling #

BioChem Press, José Luis Paz, Teresa Cusati

Motivation. Polyatomic molecules can be described by a two–level system represented by two crossed harmonic potential curves (including vibrational levels) in order to study their nonlinear signal response. The variation of the coupling parameter has an important influence on the behavior of the dipole moments and, consequently, on the polarization on the new coupled–state basis. Method. The calculation method employed is based on the Liouville formalism for the density matrix, where the conventional optical Bloch equations are solved in Fourier space to obtain the density matrix elements associated to the polarization of the system. Changes in the coupling parameters V0 (energetic difference between the minima of the potential curves), S (height to which the vibronic coupling occurs) and v (coupling parameter) produce modifications in the behavior of the dipole moments and Polarization on the coupled system. In this communication, two studies are presented: (a) variation of the parameters S and v, while keeping V0 constant and, (b) variation of S and V0, while keeping v constant. In order to study the effects of these changes, the rotating–wave approximation is neglected, which permits us to analyze the processes that occur out of the resonance region. Moreover, the permanent dipole moments of the states in the uncoupled basis are included. Results. First case (variation of S and v): an important increment of dipole moments and polarization magnitude values were observed for low values of v and high values of S. Second case (variation of S and V0): an abruptly increment in the polarization magnitude were found at high values of S and low values of V0. Conclusions. The observed changes in the nonlinear response are associated to modifications in the overlap integral and consequently to the dipole moments of the states in the new coupled basis.

•Jan 1, 2005•0 citations

Study of force constants of crossed curves on four-wave mixing signals

Teresa Cusati, José Luis Paz, Emilio Squitieri

In this work we have studied the effects on a four-wave mixing (FWM) signal of different apertures of two crossed harmonic curves in an intramolecular coupling model. These apertures are measured using the quotient between the resonant frequencies of two curves, Δ = 0 /ω 0 . We observed changes in intensity and position of the peaks present in the FWM signal spectra due to the variations in Δ. These changes are directly related to the behaviour of the resonant frequency and the dipole moments of the coupled states with the parameter Δ.

Journal of Optics A Pure and Applied Optics•Aug 21, 2003•0 citations

Study of the nonlinear optical responses in the Four-wave mixing signal in saturation regimen of a two-level system with intramolecular coupling

José Luis Paz, Eleana Ruiz-Hinojosa, Ysaías J. Alvarado +5 more

We consider the Four-Wave mixing (FWM) signal and the effects of the pump beam on the nonlinear optical responses of a two-level system where intramolecular coupling is modelled by two coupled harmonic electronic potentials, displaced both in their equilibrium minimum position and energy. We investigate the modifications introduced in the FWM signal, considering a simple representation for the vibrational structure and including molecular electronic states with nonzero permanent dipole moments. The critical quantities for this analysis are the transition and permanent dipole moments, which depend strongly on the intramolecular coupling. Our results show how both absorption and dispersion are affected by the vibronic coupling.

Journal of Modern Optics•Jun 24, 2020•3 citations
Abstract In the present work, we have studied modifications in the transition and permanent dipole moments of states in a coupled basis (including vibronic coupling) due to variations in the transition dipole moment between the uncoupled states, m 12 , as a function of the parameter δ = ω~\tilde{\omega}ω~ 0 /ω 0 (relative aperture) of the potential‐energy curves of the states involved. Modifications in the slopes of the transition and permanent dipole moments of the coupled states and changes in the magnitude of maximal intensity of the four‐wave mixing (FWM) signal are observed due to variations in these parameters. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Motivation. The spectroscopic analysis of the behavior of the nonlinear signal response of systems including electronic levels is described by the coupling parameters of crossed harmonic potential curves. Method. Changes in the Four–Wave Mixing (FWM) signal intensity are originated by the modifications of the dipole moments in the new coupled basis due to variation of the parameters V0 (energetic difference between the minima), v (coupling parameter) and G (strength constant) corresponding to the crossed states involved. The permanent dipole moments of the states in the uncoupled basis have been included and the Rotating–Wave Approximation is neglected in order to observe the processes out of the resonance region. The calculation method is based in the Liouville–von Neumann formalism for the density matrix, where the Conventional Optical Bloch Equations are solved in Fourier space to obtain the density matrix elements associated with the Macroscopic Polarization responsible of the FWM signal. Results. Variation in the coupling parameters generates modifications in the dipole moments of the coupled states. These modifications induce changes in the intensity values of the FWM signal, including the nullity of the dipole moments producing the nullity of the nonlinear signal. Mathematical expressions are obtained to interpret these results. Conclusions. Changes in the characteristic coupling parameters induce modifications on the crossed potential curves, and consequently, on the nonlinear response and intensity.
In this work we study the changes in the Four-Wave Mixing (FWM) signal with the modification of the permanent and transition dipolar moments of states in a coupled basis (under the inclusion of intramolecular coupling phenomenon), due to the changes in different parameters, such as coupling parameters v and Vo, strength constant Δ, and transition dipolar moment between the uncoupled states m12. Changes in the intensity and position of the resonances in the FWM signal spectra are observed with the variation in the parameters mentioned above.
In this work we have studied the changes in the Four-Wave Mixing (FWM) signal with the changes in the ratio between the longitudinal and transversal relation times T1/T2. Moreover, we have studied too the modifications in the FWM signal with the changes in the strength constant of the crossed harmonic potential curves that describe the two- levels system employed to this study. We have included the permanent dipolar moments of the states in the uncoupled basis. The rotating wave approximation is neglected to observe the process out of the resonance region. We observed changes in the shape, intensity and position in the resonances of the FWM signal spectra, with the changes in the ratio T1T2 and the strength constant (delta) .© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Motivation. Polyatomic molecules can be described by a two–level system represented by two crossed harmonic potential curves (including vibrational levels) in order to study their nonlinear signal response. The variation of the coupling parameter has an important influence on the behavior of the dipole moments and, consequently, on the polarization on the new coupled–state basis. Method. The calculation method employed is based on the Liouville formalism for the density matrix, where the conventional optical Bloch equations are solved in Fourier space to obtain the density matrix elements associated to the polarization of the system. Changes in the coupling parameters V0 (energetic difference between the minima of the potential curves), S (height to which the vibronic coupling occurs) and v (coupling parameter) produce modifications in the behavior of the dipole moments and Polarization on the coupled system. In this communication, two studies are presented: (a) variation of the parameters S and v, while keeping V0 constant and, (b) variation of S and V0, while keeping v constant. In order to study the effects of these changes, the rotating–wave approximation is neglected, which permits us to analyze the processes that occur out of the resonance region. Moreover, the permanent dipole moments of the states in the uncoupled basis are included. Results. First case (variation of S and v): an important increment of dipole moments and polarization magnitude values were observed for low values of v and high values of S. Second case (variation of S and V0): an abruptly increment in the polarization magnitude were found at high values of S and low values of V0. Conclusions. The observed changes in the nonlinear response are associated to modifications in the overlap integral and consequently to the dipole moments of the states in the new coupled basis.
In this work we have studied the effects on a four-wave mixing (FWM) signal of different apertures of two crossed harmonic curves in an intramolecular coupling model. These apertures are measured using the quotient between the resonant frequencies of two curves, Δ = 0 /ω 0 . We observed changes in intensity and position of the peaks present in the FWM signal spectra due to the variations in Δ. These changes are directly related to the behaviour of the resonant frequency and the dipole moments of the coupled states with the parameter Δ.
We consider the Four-Wave mixing (FWM) signal and the effects of the pump beam on the nonlinear optical responses of a two-level system where intramolecular coupling is modelled by two coupled harmonic electronic potentials, displaced both in their equilibrium minimum position and energy. We investigate the modifications introduced in the FWM signal, considering a simple representation for the vibrational structure and including molecular electronic states with nonzero permanent dipole moments. The critical quantities for this analysis are the transition and permanent dipole moments, which depend strongly on the intramolecular coupling. Our results show how both absorption and dispersion are affected by the vibronic coupling.