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).

Density functional theory study of geometry and stability of small Zrn (n = 2–10) clusters

“…The most stable structure was found to be the equilateral triangle with D 3h symmetry which is in agreement with the experimental results [9]. Previous study [15] using the CAS-MCSCF method predicted that the most stable structure for Zr 3 is the C 2v symmetry with…”

Vibrational and geometric structures of Nb3C2 and Nb3C+2 from pulsed field ionization-zero electron kinetic energy photoelectron spectra and density functional calculations

“…3 and with each other. 5 mode is the totally symmetric stretching of the Nb-Nb bonds. The 6 and 7 modes are deformation of the Nb 3 triangle.…”

“…The f n ( f 0, , f 1 , f 2 , f 3 ) bands have energies of 0Ϫ0 ϩ339 cm Ϫ1 ϩ258n cm Ϫ1 , suggesting that they are combination bands of 5 ϩ ϩn 6,7 ϩ (6 0 p 7 9 nϪp 5 0 1 ). This gives a frequency of 339 cm Ϫ1 for the ion mode 5 ϩ . The b n , d n , and g n progressions appear to be due to transitions from the excited vibrational level of a neutral mode with its frequency being 20 cm Ϫ1 smaller than that of the ion.…”

Absorption, resonance Raman, and Raman excitation spectra of hafnium trimers

“…of both Zr 3 3 and Nb 3 5 have D 3h symmetry, although in both cases there is little or no vibronic distortion. On the other hand Cu 3 10 is well known to be a fluxional molecule in the ground state and is perhaps the best model for the present case.…”

“…Ozin and MacIntosh 6 have suggested that force constants for higher clusters (n Ͼ2) may be obtained from that of the dimer by simple distribution among the various bonds and we have found this to be a reliable guide. 7,8 Assuming a central force field, the totally symmetric fundamental frequency for a trimer should be observed at approximately )/2ϭ0.866 times the dimer frequency. For dihafnium the fundamental frequency is 176 cm Ϫ1 predicting a trimer frequency of 152 cm Ϫ1 , so it is likely that the observed intervals (143-152 cm Ϫ1 ) correspond to the totally symmetric vibration.…”