Theoretical study of multiphoton processes in diatomic molecules

Abstract

AbstractWe investigate multiphoton processes in diatomic molecules. We adopt the Morse oscillator model for the vibrational state of molecules and simulate the population transfer between vibrational levels caused by molecule–laser interaction. The ground‐state energy is calculated by the quadratic configurational interaction (QCISD) level ab initio molecular orbital calculation, and the potential energy curve of the ground state is fitted by the Morse potential curve to evaluate the discrete vibrational levels. An intense laser field generally causes the nonlinear optical processes in molecules, such as multiphoton excitation and ionization. We investigate the 1‐, 2‐, 3‐, and 4‐photon absorption processes in H2 and OH molecules in relation to the laser intensity in the picosecond (ps) regime. We also apply the stimulated Raman adiabatic passage (STIRAP) method to the efficient generation of the highly vibrational excited state, using a couple of the simultaneous 2‐photon absorption processes as the Stokes and pump processes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005