ROTATIONAL ENERGY-TRANSFER IN THE NA2B(3)PI(U) STATE - PROPENSITY RULES FOR TRANSITIONS BETWEEN HYPERFINE COMPONENTS

The changes in the hyperfine quantum number (F') that accompany collision-induced DELTAJ, DELTAOMEGA, and DELTA (e/f-parity) transitions in the Na2 b 3PI(u)-state have been studied by sub-Doppler, cw, perturbation-facilitated optical-optical double resonance (PFOODR) spectroscopy. The Na2 is contained in a heat pipe oven at approximately 1 Torr and the primary collision partner is Na(3s 2S). The PUMP laser selectively excites a single b 3PI0u upsilon' = 12, J' = 43e, s or 44e, a rotational level, the parent level. All F' hyperfine components of the parent J' level are directly populated by the PUMP laser, but with different velocity projections relative to the laser propagation direction. Thus each parent hf component is labeled by its longitudinal velocity. As the PROBE laser is scanned through various 2 3PI(OMEGAg) upsilon = 2, J <-- b 3PI(OMEGA'u) upsilon'= 12, J' transitions, sub-Doppler hyperfine structure can be resolved on each parent and daughter rotational line in the PFOODR fluorescence excitation spectrum. The collisional propensity rule DELTAF = DELTAJ is obeyed for (s, a permutation symmetry conserving) DELTAJ' = 0, DELTAOMEGA' = 0, + 1, and +2 and DELTAJ' = +/- 1, +/- 2, DELTA = 0 collision-induced transitions. No systematic exploration of the parent-J', OMEGA' dependence of the DELTAF propensity was undertaken; in particular, the present study was restricted to the high-J limit where the Na2/Na collisions are not sudden relative to the rotational (half) period and where J much greater than I. The DELTAF = DELTAJ hyperfine propensity rule observed for high-J levels of the Na2 b 3PI(u) state is consistent with previous theoretical predictions of a DELTAF = 0 propensity for collision-induced DELTAJ = 0 transitions between LAMBDA-doublet components of the OH X 2PI state and a DELTAF = DELTAJ propensity for collision-induced transitions between CaBr X 2SIGMA+ rotational levels.