Time-dependent depolarization of aligned HD molecules

Abstract

An aligned sample of HD(v = 1, J = 2, M_J = 0) molecules is prepared under collision-free conditions using the S(0) stimulated Raman pumping transition. Subsequent coupling to the spins of the deuteronI_D and the proton I_H causes the initial degree of alignment to oscillate and decrease as monitored over the time range from 0–13 μs via the O(2) line of the [2 + 1] REMPIE,F¹Σ⁺_g−X¹Σ⁺_g (0,1) band. The time dependence of the rotational alignment is also calculated using both a hierarchical coupling scheme in which the rotational angular momentum J is regarded first to couple to I_D, and then the resultant F_i to couple to I_H, to form the total angular momentum F and a non-hierarchical coupling scheme in which the HD energy level structure is not assumed to be diagonal in the |I_H(JI_D)F_iFM_F> basis set. The experimental data is in good agreement with the non-hierarchical calculation but not with the hierarchical calculation, as expected for this system. Additionally, we calculate the time dependence of the H and D nuclear spin polarizations.