RESONANCE RAMAN-SPECTRUM AND EXCITATION PROFILE OF MASS-SELECTED ZIRCONIUM TRIMERS

We present the resonance Raman and Raman excitation profile of mass-se lected zirconium trimers in argon matrices. In the Raman spectra, two fundamentals and one overtone are observed. Average Raman shifts, alon g with standard deviations (in parentheses) are 176.7 (13) cm(-1) (nu( 2)), 258.0 (12) cm(-1) (nu(1)), and 516.1 (8) cm(-1) (2 nu(1)). The ra tio of the frequencies of the two lowest lines (nu(1) nu(2)) is 1.46, which is very close to root 2. This is indicative of a symmetrical equ ilateral geometry (D-3h). In such a case we expect two normal frequenc ies, one for a totally symmetric stretch of symmetry a'(1)(nu(1)) and a doubly degenerate bend of symmetry e'(nu(2)). The Raman excitation p rofiles of the nu(1)(a'(1)) line shows two broad maxima: one near 491 nm and the other near 614 nm. The nu(2)(e') profile shows a broad regi on of intensity only near 614 nm. With the aid of theory we assign the 614 nm band to be (1)A'(1)-(1)E' (x,y polarized) while the 491 nmband must be (1)A'(1)-(1)A''(2) (Z polarized). (C) 1995 American Institute of Physics.