Abstract
High resolution spectra of the B E-2-X (2)A(1) transitions of CaBH4 and SrBH4 have been recorded using laser excitation spectroscopy in a laser ablation/molecular jet source. Because of rotational cooling in the molecular jet and nuclear spin statistics, transitions arising from only the K-'=1 <- K ''=0, K-'=2 <- K ''=1, and K-'=0 <- K ''=1 subbands have been observed. For each molecule, an analysis of the data using E-2 and (2)A(1) symmetric top Hamiltonians yielded rotational, spin-orbit, and spin-rotation parameters for the observed states. For both molecules the rotational constants compare well with those calculated for a tridentate borohydride structure. A large reduction in the spin-orbit splitting and in the metal-ligand separation for each molecule indicates an increase in the amount of d atomic orbital character in the first excited E-2 states of the monoborohydrides as compared to the monomethyl derivatives. For each molecule no evidence of internal rotation of the BH4- ligand was found. A change in the magnitude and sign of the spin-rotation constant epsilon(1) confirms an energy reordering of the first excited E-2 and (2)A(1) states in both CaBH4 and SrBH4 as compared to CaCH3 and SrCH3. The data also suggest that the B E-2(1/2) rotational energy levels of CaBH4 may be perturbed by a vibronic component of the A (2)A(1) state. (c) 2007 American Institute of Physics.
| Original language | English |
|---|---|
| Pages (from-to) | - |
| Number of pages | 10 |
| Journal | Journal of Chemical Physics |
| Volume | 126 |
| Issue number | 16 |
| DOIs | |
| Publication status | Published - 28 Apr 2007 |
Keywords
- ALKALI-METAL TETRAHYDROBORATE
- EXCITED VIBRATIONAL-STATES
- ROTATIONAL ENERGY LEVELS
- MICROWAVE-SPECTRUM
- ELECTRONIC SPECTROSCOPY
- ABINITIO CALCULATION
- GEOMETRIC STRUCTURE
- COMPLEX HYDRIDES
- INTERNAL MOTION
- MOLECULES