Nonadiabatic laser-induced orientation and alignment of rotational-state-selectedCH3Brmolecules

Abstract

Nonadiabatic orientation and alignment of hexapole rotational-state-selected methyl bromine $({\mathrm{CH}}_{3}\mathrm{Br})$ molecules is studied. The temporal evolution of the mixed dc field and laser-induced orientation and alignment is measured by a pump-probe method. The temporal orientation and alignment transients are in good agreement with the time-dependent Schr\"odinger equation calculation we perform. We show that the degree of orientation and alignment is strongly dependent on the selected initial rotational state. The temporal transients originating from two different initial states, the $|111\ensuremath{\rangle}$ state and the mixed $|111\ensuremath{\rangle}+|212\ensuremath{\rangle}$ state, are discussed. Our results show a maximum degree of $\ensuremath{\langle}cos\ensuremath{\theta}\ensuremath{\rangle}=\ensuremath{-}0.7$ for the orientation of ${\mathrm{CH}}_{3}\mathrm{Br}$ molecules in the $|111\ensuremath{\rangle}$ state.