Characterization of isolated Ga2 molecules by resonance Raman spectroscopy and variations of Ga-Ga bonding

Isolated Ga-2 dimers were characterized in an argon matrix with the aid of resonance Raman and UV/ Vis spectroscopy. The resonance Raman spectra gave evidence of not only the v(Ga-Ga) fundamental, but also four overtones. Each of the signals exhibits Ga-69/Ga-71 isotopic splitting leading to the triplet pattern characteristic of two equivalent Ga atoms. On the basis of the experimental data, a harmonic frequency and anharmonicity constant have been determined for Ga-2. An estimate of the dissociation energy on the assumption of a Morse-type potential energy curve results in a D-e value (upper limit) of about 145 kJ mol(-1). The force constant (64.8 +/- 0.3 N m(-1)) and dissociation energy of Ga-2 are compared with those of other diatomics and those of molecules featuring Ga-Ga bonds.