Coherent destruction of tunneling in a six-dimensional model of NHD2: a computational study using the multi-configuration time-dependent Hartree method.

Abstract

We investigate the phenomenon of coherent destruction of tunneling in a six-dimensional model of the NHD2 molecule. Two regimes are considered for the frequency of the laser field. A non-resonant regime where the frequency of the laser field is high with respect to the ground vibrational state tunneling splitting but smaller than the transition frequencies between the ground and excited vibrational states; and a quasi-resonant regime where the frequency of the laser field is close to the transition frequency between the ground and first excited vibrational states. In each case, we study the laser driven dynamics in the framework of the Floquet formalism and derive simple analytical formulas that explain the shape of the quasienergy curves associated with the two tunneling components of the ground vibrational state. This analysis allows us to obtain the parameters (frequency and amplitude) of the laser field that lead to the coherent destruction of tunneling. The multi-configuration time-dependent Hartree method is then used to solve the time-dependent Schrödinger equation for a six-dimensional model of the molecule in interaction with an adiabatically turned on monochromatic laser field, in order to confirm the results obtained from this analysis.