Chapter 6
Weakly-Bound Complexes and Clusters
Abstract This chapter deals with a comprehensive class of weakly bound complexes
and clusters. This book is devoted to gas-phase photoprocesses, that is, electronically
excited states only those weakly-bound complexes that are weakly-bound in electronically excited states, as well, are considered. The complexes with so-called
hydrogen and halogen bonds in the ground state will be considered briefly. The
spectroscopic characteristics of the R g X 2 ðX0
þ
g ; B0
þ
u ; E0
þ
g Þ, X = Cl, Br, I, and RgICl
(X0
+
, A1, B0
+ , E0
+
, b1, D'2) states and the complex electronically-excited states
dynamics are discussed very thoroughly. The ArICl(X0
+
, A1, E0
+
, b1, D'2), NeIBr
(X0
+
, A1, E0
+
, b1) spectroscopic characteristics, and dynamics of these complexes in
IP states are discussed, also. The data, concerning the vdW complexes of iodine
molecules with diatomic molecules, in the IP states, in particular, are considered. The
Rg n X 2 , n > 1, and HeNeI 2 (X0
+
, A1, E0
+ , b1) spectral parameters, and their excited
state dynamics, are analyzed. And finally, the vdW complexes of Rg and metal atoms
are briefly considered.
6.1 Definitions
As it was mentioned in 1973 [1], ‘A precise definition of the term molecular
complex is not easy; and Person attempted to provide one as follows:’
A molecular complex between two molecules is an association, somewhat stronger than
ordinary van der Waals associations, of definite stoichiometry …. The partners are often
already closed-shell (saturated valence) electronic structures. In loose complexes, the
identities of the original molecules are, to a large extent, preserved [2].
The definitions of even van der Waals (vdW) complexes and forces differed from
each other earlier:
Van der Waals molecules are weakly bound complexes of small atoms or molecules held
together, not by chemical bonds, but by intermolecular attractions [3].
© Springer Nature Switzerland AG 2021
A. Pravilov, Gas-Phase Photoprocesses, Springer Series in Chemical Physics 123,
https://doi.org/10.1007/978-3-030-65570-9_6
199
Weakly-Bound Complexes and Clusters
Abstract This chapter deals with a comprehensive class of weakly bound complexes
and clusters. This book is devoted to gas-phase photoprocesses, that is, electronically
excited states only those weakly-bound complexes that are weakly-bound in electronically excited states, as well, are considered. The complexes with so-called
hydrogen and halogen bonds in the ground state will be considered briefly. The
spectroscopic characteristics of the R g X 2 ðX0
þ
g ; B0
þ
u ; E0
þ
g Þ, X = Cl, Br, I, and RgICl
(X0
+
, A1, B0
+ , E0
+
, b1, D'2) states and the complex electronically-excited states
dynamics are discussed very thoroughly. The ArICl(X0
+
, A1, E0
+
, b1, D'2), NeIBr
(X0
+
, A1, E0
+
, b1) spectroscopic characteristics, and dynamics of these complexes in
IP states are discussed, also. The data, concerning the vdW complexes of iodine
molecules with diatomic molecules, in the IP states, in particular, are considered. The
Rg n X 2 , n > 1, and HeNeI 2 (X0
+
, A1, E0
+ , b1) spectral parameters, and their excited
state dynamics, are analyzed. And finally, the vdW complexes of Rg and metal atoms
are briefly considered.
6.1 Definitions
As it was mentioned in 1973 [1], ‘A precise definition of the term molecular
complex is not easy; and Person attempted to provide one as follows:’
A molecular complex between two molecules is an association, somewhat stronger than
ordinary van der Waals associations, of definite stoichiometry …. The partners are often
already closed-shell (saturated valence) electronic structures. In loose complexes, the
identities of the original molecules are, to a large extent, preserved [2].
The definitions of even van der Waals (vdW) complexes and forces differed from
each other earlier:
Van der Waals molecules are weakly bound complexes of small atoms or molecules held
together, not by chemical bonds, but by intermolecular attractions [3].
© Springer Nature Switzerland AG 2021
A. Pravilov, Gas-Phase Photoprocesses, Springer Series in Chemical Physics 123,
https://doi.org/10.1007/978-3-030-65570-9_6
199