cases (Table 6.9). The Dv E = 1 propensity rule is valid in these cases, and the
luminescence at Dv E = 0 VP is ascribed to the NeI 2 (E,v E ,n E ) complexes themselves
(6.3.13) (see below).
The RgI 2 (E) state couples with other bound RgI 2 (IP) states, and EP mechanism
has to be sufficiently different from that of the RgI 2 (B) state.
Two possible mechanisms of EP may occur after RgI 2 (E,v E ,n E ) population:
direct coupling of the initially excited bound RgI 2 (E,v E ,n E ) with a quasi-continuum
Rg + I 2 (IP,v IP ) (‘direct EP’) or a sequential non-adiabatic RgI 2 (E ! IP) transition
with the following VP of the RgI 2 (IP) including IVR (‘EP + IVR’).
The principal channel for the HeI 2 (E) and NeI 2 (E) EP is RgI 2 (E) ! Rg + I 2 (D,
v D ). Taking into account only pairwise u–g interactions between IP states in DIM
PT1 model, the RgI 2 (E ! D) EP channel is forbidden in the T-shaped configuration [105]. However, a contribution of this channel among all EP channels is >
70% in the experiments (see Table 6.9). Non-adiabatic coupling between all the IP
states is allowed in the bent configuration (C s symmetry group). Averaging of the
interaction matrix elements over bending h angle gives non-zero
NeI 2 (E * D) coupling. Therefore, one can believe that the DIM PT1 model is
capable of describing NeI 2 PESs and energies of vdW levels, but unable to describe
nonadiabatic processes.
The experimental vibrational distributions of the I 2 (D,v D ) EP products are
described in the energy-gap law [97]
P v D
ð Þ$e
ÀaDE
;
ð6:3:15Þ
where P(v D ) is the probability of a population of the D,v D vibronic state, a is a
fitting parameter, and DE is an energy gap between the initial NeI 2 (E,v E ,n E ) and
final I 2 (D,v D ) levels (see Fig. 6.18).
Luminescence of the NeI 2 (E) complexes. Luminescence similar to that of I 2 (E,v E )
corresponding to Dv E = 0 occurs at the v E = 0-2 groups (see Fig. 6.22, as an
example), though the NeI 2 (E,v E ,n E ) ! Ne + I 2 (E,v E ) (Dv E = 0) VP channels are
energetically closed. The lifetimes of a luminescence species at k lum = 4297 Å
corresponding to the v E = 0-2 groups differ significantly: it is similar to the
I 2 (E,0! B) transition radiative lifetime, s % 26 ns for the v E = 1, 2, and much less
for v E = 0 one, s = (8.0 ± 0.5) ns (Fig. 6.23).
The only open channels of the NeI 2 (E,0,n E ) decay are EP (6.3.12), and luminescence of the complex (6.3.13). Therefore, luminescence, k lum = 4000–4400 Å,
has to be assigned to luminescence of the complex itself so the lifetime of the
NeI 2 (E,0,n E ) complex is 8 ns, and the total rate of the complex decay is equal to
12.5Á10
7 s
−1 . The total rate of the EP channels (6.3.12), is k 3.12 = (7.8–8.8)∙10
7 s
−1 ,
s EP % 12 ns (see data on NeI 2 (E,0,n E ) in Table 6.9), and the radiative decay rate of
the NeI 2 (E,0,0) vdW complex is k 3.13 = (3.8– 4.8)Á10
7 s
−1 , similar to that of
I 2 (E, 0). The NeI 2 (E,0,n E ) EP proceeds slowly, since light Ne atom perturbs a I 2
molecule weakly. The maximum of the I 2 (D, v D ! X) luminescence temporal
6.3 Van der Waals Complexes
231
luminescence at Dv E = 0 VP is ascribed to the NeI 2 (E,v E ,n E ) complexes themselves
(6.3.13) (see below).
The RgI 2 (E) state couples with other bound RgI 2 (IP) states, and EP mechanism
has to be sufficiently different from that of the RgI 2 (B) state.
Two possible mechanisms of EP may occur after RgI 2 (E,v E ,n E ) population:
direct coupling of the initially excited bound RgI 2 (E,v E ,n E ) with a quasi-continuum
Rg + I 2 (IP,v IP ) (‘direct EP’) or a sequential non-adiabatic RgI 2 (E ! IP) transition
with the following VP of the RgI 2 (IP) including IVR (‘EP + IVR’).
The principal channel for the HeI 2 (E) and NeI 2 (E) EP is RgI 2 (E) ! Rg + I 2 (D,
v D ). Taking into account only pairwise u–g interactions between IP states in DIM
PT1 model, the RgI 2 (E ! D) EP channel is forbidden in the T-shaped configuration [105]. However, a contribution of this channel among all EP channels is >
70% in the experiments (see Table 6.9). Non-adiabatic coupling between all the IP
states is allowed in the bent configuration (C s symmetry group). Averaging of the
interaction matrix elements over bending h angle gives non-zero
NeI 2 (E * D) coupling. Therefore, one can believe that the DIM PT1 model is
capable of describing NeI 2 PESs and energies of vdW levels, but unable to describe
nonadiabatic processes.
The experimental vibrational distributions of the I 2 (D,v D ) EP products are
described in the energy-gap law [97]
P v D
ð Þ$e
ÀaDE
;
ð6:3:15Þ
where P(v D ) is the probability of a population of the D,v D vibronic state, a is a
fitting parameter, and DE is an energy gap between the initial NeI 2 (E,v E ,n E ) and
final I 2 (D,v D ) levels (see Fig. 6.18).
Luminescence of the NeI 2 (E) complexes. Luminescence similar to that of I 2 (E,v E )
corresponding to Dv E = 0 occurs at the v E = 0-2 groups (see Fig. 6.22, as an
example), though the NeI 2 (E,v E ,n E ) ! Ne + I 2 (E,v E ) (Dv E = 0) VP channels are
energetically closed. The lifetimes of a luminescence species at k lum = 4297 Å
corresponding to the v E = 0-2 groups differ significantly: it is similar to the
I 2 (E,0! B) transition radiative lifetime, s % 26 ns for the v E = 1, 2, and much less
for v E = 0 one, s = (8.0 ± 0.5) ns (Fig. 6.23).
The only open channels of the NeI 2 (E,0,n E ) decay are EP (6.3.12), and luminescence of the complex (6.3.13). Therefore, luminescence, k lum = 4000–4400 Å,
has to be assigned to luminescence of the complex itself so the lifetime of the
NeI 2 (E,0,n E ) complex is 8 ns, and the total rate of the complex decay is equal to
12.5Á10
7 s
−1 . The total rate of the EP channels (6.3.12), is k 3.12 = (7.8–8.8)∙10
7 s
−1 ,
s EP % 12 ns (see data on NeI 2 (E,0,n E ) in Table 6.9), and the radiative decay rate of
the NeI 2 (E,0,0) vdW complex is k 3.13 = (3.8– 4.8)Á10
7 s
−1 , similar to that of
I 2 (E, 0). The NeI 2 (E,0,n E ) EP proceeds slowly, since light Ne atom perturbs a I 2
molecule weakly. The maximum of the I 2 (D, v D ! X) luminescence temporal
6.3 Van der Waals Complexes
231