Resonance Raman spectrum and excitation profile of mass-selected zirconium trimers

Abstract

We present the resonance Raman and Raman excitation profile of mass-selected zirconium trimers in argon matrices. In the Raman spectra, two fundamentals and one overtone are observed. Average Raman shifts, along with standard deviations (in parentheses) are 176.7 (13) cm−1 (ν2), 258.0 (12) cm−1 (ν1), and 516.1 (8) cm−1 (2ν1). The ratio of the frequencies of the two lowest lines (ν1/ν2) is 1.46, which is very close to √2. This is indicative of a symmetrical equilateral geometry (D3h). In such a case we expect two normal frequencies, one for a totally symmetric stretch of symmetry a′1 (ν1) and a doubly degenerate bend of symmetry e′(ν2). The Raman excitation profiles of the ν1(a′1) line shows two broad maxima: one near 491 nm and the other near 614 nm. The ν2 (e′) profile shows a broad region of intensity only near 614 nm. With the aid of theory we assign the 614 nm band to be 1A′1−1E′ (x,y polarized) while the 491 nm band must be 1A′1−1A″2 (z polarized).