The HeBr 2 (B, v B ) complex undergoes VP and EP [75, 76, 82, 83]. The
He
79 Br 2 (B, v B ) complex lifetimes have been measured in the v B = 10-20 [83], 16–
23 [76] and 34-48 [75] ranges. The lifetime decreases from 157 ps (v B = 10) to
1.8 ps (v B = 44) and there are some features in this dependency:
There are sharp decrease of the lifetime at v B = 11, 13, 14 due to EP rate increase
caused by the He
79 Br 2 (B, v B ) ! He
79 Br 2 (
3 P(1 g , 2 g )) ! He +
79 Br +
79 Br predissociation. The EP rate is (0–15)% of total predissociation rate except those at
v B = 11, 13, 14 [83];
VP rate decrease at v B = 45 due to the Dv B = 1 VP channel [75].
Below v B = 43, the VP product rotational distribution for the Dv B = 1, 2 VP
channels are similar [82].
(a)
(b)
Fig. 6.7 The He
79
Br 2 (B,v B = 12) (a) and He
79
Br 2 (X,v X = 0) (b) adiabatic potentials (black lines),
plotted as a function of h (see Fig. 6.1). Superimposed on the potentials are the probability
amplitudes of the lowest-energy vdW vibrational eigenstates. Each state is plotted so that zero
amplitude corresponds to the energy of the level. The state localized in the linear wells are shown
as solid lines, those localized in the T-shaped minimum as dashed lines, and the free rotor states are
plotted as dotted lines (see [74]) (Reproduced from D.S. Boucher, D.B. Strasfeld, R.A. Loomis, J.
M. Herbert, S.E. Ray, A.B. McCoy, J. Chem. Phys. 123, 104312 (14 pp) (2005). https://doi.org/
10.1063/1.2006675. https://doi.org/10.1063/1.2006675 with the permission of AIP Publishing)
6.3 Van der Waals Complexes
213