Bhupat Sharma

Multiphoton rovibrational excitation of diatomic molecules in the presence of an intense infrared laser beam using a non-perturbative quasi-energy technique

A non-perturbative quasi-energy method has been developed to compute the rovibrational multiphoton excitation transition probabilities in diatomic (heteronuclear) molecules (in the electronic ground state) in the presence of an intense infrared laser beam. As the Floquet analysis is quite demanding computationally the authors therefore have resorted to a new non-perturbative quasi-energy method which not only reduces the computer time to a reasonable scale but also provides useful physical insights for the understanding of multiphoton absorption (MPA) dynamics. The practicability of this method is illustrated by computing the MPA spectra for OH, CO and HF molecules. The authors have compared their results with those obtained by exact Floquet and non-adiabatic Floquet analysis. A number of interesting features such as line broadening, dynamic Stark shift, hole-burning, etc., have been studied as a function of laser frequency and intensity.

Laser induced vibration–rotation excitation of hydroxyl ions: OH− and OH+

The quantum dynamics of vibration–rotation excitation of hydroxyl ions (e.g., OH− and OH+ in the gaseous phase) in the presence of a laser beam is investigated. The nonperturbative Floquet method is used to solve the equation of motion with an explicitly time‐dependent Hamiltonian. Convergent results are obtained for the long‐time averaged transition probabilities for various transitions by including a sufficiently large number of rovibrational and photon states. In order to understand the roles played by power broadening, dynamic stark shifts, and non‐Lorentzian line shapes, higher laser intensities (in the GW/cm2 range) are considered in the molecular excitation process.

Excitation of atomic hydrogen due to proton impact in the presence of a resonant laser field

The collision of a proton with a hydrogen atom in the presence of electromagnetic radiation which is nearly resonant with the atomic levels is investigated theoretically. The non-perturbative quasi energy method is used to describe the laser-atom interaction and the proton-dressed atom collision is solved using a diagonalization technique. We have calculated the transition probabilities and the total cross-section for various transitions. We discuss the influence of various laser and collision parameters on the excitation process.

Multiphoton vibration-rotation excitation of SH, SH- and SH+ ions

The Floquet method (non-perturbative) is used to investigate the multiphoton vibration-rotation excitation of SH, SH- and SH+ ions in the presence of an intense infrared laser beam. A number of interesting features such as line broadening and the dynamic Stark shift are studied as a function of laser intensity and frequency.

Vibrational excitation of the OH molecule by proton (H+) impact in the presence of an infrared laser beam: a non-perturbative technique

The general theory of vibrational excitation of a diatomic OH molecule due to collision with a proton (H+) in the presence of an infrared laser beam, using the quasi-energy approach (non-perturbative) is presented. The vibrational transition probability and the excitation cross section are calculated for different field intensities and the effect of the collision on the radiative excitation process is investigated by changing the various collision parameters and using different values of the molecular field detunings.

Multiphoton vibration-rotation excitation of the OH molecule in the presence of an infrared laser beam

Abstract The Floquet method (non-perturbative) is used to investigate the multiphoton vibration—rotation excitation of the OH molecule in the presence of an infrared laser beam. A number of interesting features, such as line broadening and the dynamic Stark shift, are studied as a function of laser intensity and frequency.

Ion-dipole interaction in the presence of an infrared laser beam

A general theory of excitation of a diatomic molecule due to collision with an ion, e.g. the H+ + HF system, in the presence of an infrared laser beam using the quasi-energy approach (non-perturbative) is presented. The effect of collision on the radiative excitation process is investigated by changing the various collision parameters with different values of molecule field detunings.

Vibrational energy transfer in collinear COCO collisions in the presence of an infrared laser beam

Abstract A simple approximate method for the vibration—vibration (V—V) energy-transfer process during collinear collision of two CO molecules in the presence of an infrared laser beam using a quasi-energy approach (non-perturbative) is presented. The effect of radiation on V—V process is investigated by changing molecular field detuning and power for various values of collision velocities.

Rovibrational excitation of a diatomic molecule due to ion impact in the presence of IR laser beam

A theoretical study is made of rovibrational excitation of a CO molecule due to proton impact in the presence of an infrared laser beam taken in the electric dipole approximation. Non-perturbative quasi-energy method has been applied to describe laser-molecule interaction. Effect of laser and collision parameters on cross-section is investigated. To show the effect of laser on collision process we have compared our results with field free results.

Interaction of electromagnetic field with the OH radical: A non-perturbative approach

A non-perturbative approach for the study of the interaction of a hydroxyl (OH) radical with infra-red radiation is presented. The dressed states and vibrational transition probability of OH radical are defined by a quasi-energy approach (non-perturbative).