Energy transfer dynamics in the A(0_u~+) state of Bi_2

摘要

Laser induced fluorescence, pulsed and CW, techniques have been used to study energy transfer within the A(0_u~+) state of Bi_2. In particular, electronic quenching in the vibrational levels near predissociation, v'= 18-25, have been examined for rare gas and nitrogen collision partners. The quenching from non-predissociated levels is independent of vibrational state and are rather rapid, 2.3―8.5 x 10~(-11) cm~3/molecule-s for v'=22. The quenching from the first significantly predissociated level, v'=23, is even faster with rate coefficients ranging from 7.4―15.7 x 10~(-11) cm~3/molecule-s. Heterogeneous predissociation is very rapid for 21≤ v' ≤39, with rates,Γ= k_(pd)(v') J (J+l), of k_(pd) as large as 1.5 x 10~5 s~(-1). Vibrational-to-translational energy transfer probabilities for the lowest vibrational levels, v'=0-4, range from 0.75―1.75% per collision, considerably lower than would be anticipated for these highly non-adiabatic collisions. Spectrally resolved emissions from collisionally populated rotational levels of Bi_2(A,v'=l) were observed for helium, neon and argon collision partners after laser excitation of the high rotational levels J'=171, 201, and 231. Total rotational removal rates from the initially prepared state range from 2.8―8.9 x 10~(-10) cm~3/molecule-s. Collisional population of rotational states with |ΔJ| ≤ 56 was observed at pressures of 0.09―1.4 torr. The state-to-state rates are adequately modeled by the energy based statistical power gap law.