The studies have shown the following:
1. No HeI 2 D; D
0
B
ð
Þtransitions in the excitation spectra have been observed
though they are allowed at the C 2v symmetry group. It means that the propensity
rules for the HeI 2 (IP − B) transitions are the same as selection rules for the
isolated I 2 molecule, and it may be deduced that the He atom behaves as a
‘spectator’ without significant perturbations of the ‘pure’ I 2 (IP) states (see [62]
and references). The same feature is observed in all the studied RgI 2 (IP ← B)
transitions in the T-shaped configuration.
2. The binding energy of the HeI 2 (E, v E = 0−17, n E = 0) do not vary with v E = 0
−17, and equal to D
E
0 ¼ 13:9 1
ð Þ cm
À1 .
3. The
HeI 2 E; v E ; n E ¼ 0
ð
Þ!He þ I 2 E; v E À Dv E
ð
Þ ;
ð6:3:3Þ
Dv E = 1, VP and
Fig. 6.12 Experimental (black line) and simulated luminescence spectra in the k lum = 2800– 4400
Å spectral range measured at the m 2 = 25025.8 cm
−1
, the HeI 2 E; 12; n E ¼ 0
hm2 B; 16; n B ¼ 0
transition (see Fig. 6.11). Spectral resolution FWHM = 10 Å. The experimental spectrum is offset
for clarity. The k 2 laser line is marked (see Table 6.5)
6.3 Van der Waals Complexes
219