Electronic spectroscopy of the alkaline-earth halide cluster Ca2Cl3

A visible spectrum of the cluster Ca2Cl3 was observed from 651 to 630 nm by 1 + 1' resonant multiphoton ionization spectroscopy. Spectra were obtained for each of the four isotopomers: Ca-2 Cl-35(3), Ca-2 Cl-35(2) Cl-37, Ca-2 Cl-35 Cl-37(2), and Ca-2 Cl-37(3). The spectra were composed of a strong o rigin band at 15 350.8 cm(-1) and several very weak vibronic bands. All of the bands were sharp with partially resolved rotational band contours. Dens ity functional calculations predicted three minimum energy isomers. The spe ctrum was assigned to the B-2(2)<--<(X)over tilde> (2)A(1) transition of th e lowest energy isomer, a planar C-2v structure having a ring of two Cl and two Ca atoms and a terminal Cl atom. The ring isomer of Ca2Cl3 has the unp aired electron localized on one Ca2+ ion to form a Ca+ chromophore. The two other predicted isomers, a D-3h trigonal bipyramid and a C-2v planar V-sha ped structure, were not consistent with the observations. (C) 2001 American Institute of Physics.