Raman spectroscopic studies on matrix-isolated arsenic and antimony molecules As4 and Sb4 in noble gas matrices

The Raman spectra of As4 and Sb4 molecules have been studied in neon, argon, krypton, and xenon matrices at 7 K. The vibrational frequencies of the As4 molecule are up to 17 cm−1 higher than the experimental gas phase data. This evident blue-shift is not caused by matrix effects but originates from an underestimation of the fundamentals in the gas phase as a course of the elevated temperatures. The observed frequencies of As4 and Sb4 show a linear dependence toward the matrix host polarizability. Extrapolated values for zero polarizability which best represent a free molecule, are considered fundamental frequencies. The general valence force fields of As4 and Sb4 were calculated from the extrapolated frequencies.