excitation band maximum of the uncomplexed I 2 very near to the bandhead). The
vdW progressions (n B = 0,1, and 2) were also identified in HeNeI 2 (B,v B ). It was
shown that all complexes required at least one I 2 (B) stretching quantum per rare gas
atom for complete decay. Larger clusters tended to require more vibrational quanta
per rare gas atom to decay. The Morse potential parameters, x e = 21.71(31),
x e x e = 0.81(0.11), D e = 88.1(5.4), D 0 = 76.2(5.6) were determined for the
HeNeI 2 (B,v B = 21) state. The HeNeI 2 (B,v B = 12) and Ne 2 I 2 (B,v B = 12) lifetimes
are * 100 ps [103]. The probabilities of the
Ne 2 I 2 B; v B ¼ 21; 22
ð
Þ!. . . ! Ne þ Ne þ I 2 B; v B À Dv B
ð
Þ ;
ð6:4:3Þ
decay are * 0.55, 0.41, 0.04, and 0.002 (v B = 21), and * 0.45, 0.47, 0.07, and
0.01 (v B = 22) for the Dv B = 2, 3, 4, and 5 channels, respectively [103].
Detailed studies of real-time dynamics of the Ne n I 2 (B,v B ) cluster, n = 2–4, in the
picosecond time scale have been carried out by A.H. Zewail and his team [129].
The authors have concluded that the dynamics does not follow a simple sequential
mechanism corresponding to direct predissociation:
Ne 2 I 2 B; v B
ð
Þ!2Ne þ I 2 B; v B À Dv B
ð
Þ ;
ð6:4:4Þ
the presence of IVR has been invoked to account the Dv B = 3 channel. The Dv B = 2
channel proceeds via sequential direct VP.
According to [131], the mechanism of the Ne 2 I 2 (B,v B ) VP can be described, as it
is done in Fig. 6.40.
Spectroscopic studies of the HeNeI 2 cluster have been carried out using the
two-step two-color
Fig. 6.40 The Ne 2 I 2 (B, v B ) vibrational predissociation (see [130]) (Reproduced from A. Bastida,
J. Zuñiga, A. Requena, N. Halberstadt, J. A. Beswick,. J. Chem. Phys. 109, 6320–6328 (1998).
http://doi.org/10.1063/1.477274 with the permission of AIP Publising)
252
6 Weakly-Bound Complexes and Clusters