Two-frequency IR laser orientation of polar molecules.
Numerical Simulations for HCN
C. M. Dion1,2, A. D. Bandrauk1, O. Atabek2, A. Keller2, H. Umeda3, and Y. Fujimura3
1Laboratoire de Chimie Théorique, Faculté des
Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada,
J1K 2R1
2Laboratoire de Photophysique Moléculaire du CNRS,
Bâtiment 213, Université Paris-Sud, 91405 Orsay, France
3Graduate School of Science, Tohoku University, Sendai 980-8578,
Japan
Using ab initio nuclear-coordinate-dependent dipole moments and polarizabilities, we study the orientation dynamics of HCN, by numerically solving the time-dependent Schrödinger equation, in the presence of a superposition of intense, linearly-polarized infrared laser pulses of frequency w and 2w. We show that polarizability acts in concert with permanent dipole moments to orient polar molecules, as opposed to alignment which occurs alone with a single laser frequency or one moment only (permanent or induced). Optimal orientation occurs for the field configuration E(t) = E0(t) (cos wt + 0.5 cos 2wt), where 2w is resonant with a 0->1 vibrational transition and E0(t) is a picosecond pulse.
Published in Chemical Physics Letters 302, 215-223
(1999).
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