Ta

180.95 amu

dimer vibrational frequency = 300.2 cm-1

dimer force constant = 4.80 mdyne/Å

References

"Spectroscopy of Mass-Selected Tantalum Dimers in Argon Matrices"

Z. Hu, B. Shen, and D. M. Lindsay,

J. Chem. Phys., 96,8757 (1992).

Abstract

The The absorption ("scattering depletion") and Raman spectra of tantalum dimers in an argon matrix have been measured for the first time. The principal absorption band of the dimer (maximum at 480 nm) shows a vibrational progression with wo' = 260 (15) cm-1 and To<=21,330 (20) cm-1. Weaker absorptions are observed between 200 and 350 nm and in the region 550-700 nm. Raman spectra (obtained by exciting into the 480 nm band) give we" = 300.2 (12) cm-1 with wece" = 1.2(2) cm-1.

Ta3 & Ru3

ke = 2.25 mdyne/Å (Ta3)
ke = 1.86 mdyne/Å (Ru3)

"Raman Spectra of Ruthenium and Tantalum Trimers
in Argon Matrices"

Li Fang, Xiaole Shen, Xiaoyu Chen, John R. Lombardi
Chemical Physics Letters, 332, 299 (2000)

Department of Chemistry and
Center for Analysis of Structures and Interfaces (CASI)
The City College of New York (CCNY), New York, NY10031
 

ABSTRACT

The resonance Raman spectra of ruthenium trimers (Ru3) in argon matrices have been obtained. Three resonance Raman transition lines were observed between 570 nm and 590 nm. Two of them (303.4 cm-1 and 603.7 cm-1) are assigned to the totally symmetric vibrational progression, giving ke = 1.86 mdyne/Å. The line at 581.5 cm-1 is assigned as the origin of a low-lying electronic state.

We also report on the observation of a resonance Raman spectrum of tantalum trimers (Ta3). Observed lines include 251.2 cm-1 and 501.9 cm-1 which we assign to the fundamental and the first overtone of the symmetric stretch in Ta3. This gives ke = 2.25 mdyne/Å.

Fig. 1   Ru3 Spectrum
 

Fig. 2   Ta3 Raman Spectrum


 
Ta4

"Absorption and Raman Spectroscopy of Mass-selected Tantalum Tetramers in Argon Matrices"

Huaiming Wang, Robert Craig, Hanae Haouri, Jian-Guo Dong, Zhendong Hu,

Alberto Vivoni, John R. Lombardi, and D.M. Lindsay,

J.Chem.Phys., 103, 3289 (1995).

Abstract

We have examined both the absorption and resonance Raman spectra of mass-selected Ta tetramers. The tetramers are produced in a sputtering source and mass filtered with a Wien filter, then neutralized and deposited in an Ar matrix at low temperatures. The absorption spectrum indicates two broad transitions, one in the red at 768 nm and another to the blue at 532 nm. Raman resonances could be excited in both regions giving three distinct fundamental frequencies at 270.2(1) cm-1, 185.1(1) cm-1, and 130.6(2) cm-1. The lowest vibration shows a long progression (up to seven overtones) with alternating separations of 135 cm-1 and 126 cm-1, indicative of a weak Jahn-Teller effect in the tetramer ground state. This, along with the observation that the fundamental frequency ratios are close to 2:sqrt(2):1 indicate that the molecule has a tetrahedral ground state geometry with an electronic E state symmetry. The appearance of three fundamentals in the resonance Raman spectrum indicates that both excited states corresponding to the observed absorption bands arise from severely distorted T electronic states.

Fig. 3   Ta4 Raman Spectrum
 

Table. Observed and predicted force constants (mdyne/Å) for dimer, trimer and tetramer of Ta. Predictions use the scheme of: G.A.Ozin and D.F. McIntosh, J. Phys. Chem., 90, 5756 (1986).

Ta Clusters
Observed
Predicted
Ta2
4.80
(4.80)
Ta3
2.25
2.40
Ta4
1.89
1.60

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