Electronic spectroscopy of the alkaline-earth halide cluster Ca2Cl3

A visible spectrum of the cluster Ca2Cl3 was observed from 651 to 630 nm by 1118 resonant multiphoton ionization spectroscopy. Spectra were obtained for each of the four isotopomers: Ca2 Cl3, Ca2 Cl2 Cl, Ca2 Cl Cl2, and Ca2 Cl3. The spectra were composed of a strong origin band at 15 350.8 cm and several very weak vibronic bands. All of the bands were sharp with partially resolved rotational band contours. Density functional calculations predicted three minimum energy isomers. The spectrum was assigned to the B2←X̃ A1 transition of the lowest energy isomer, a planar C2v structure having a ring of two Cl and two Ca atoms and a terminal Cl atom. The ring isomer of Ca2Cl3 has the unpaired electron localized on one Ca 21 ion to form a Ca chromophore. The two other predicted isomers, a D3h trigonal bipyramid and a C2v planar V-shaped structure, were not consistent with the observations. © 2001 American Institute of Physics. @DOI: 10.1063/1.1353547#