TITLE

A high-resolution analysis of the A 2A’–X 2A’ transition of CaSH by laser excitation spectroscopy

AUTHOR(S)
Jarman, C. N.; Bernath, P. F.
PUB. DATE
May 1993
SOURCE
Journal of Chemical Physics;5/1/1993, Vol. 98 Issue 9, p6697
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The high resolution spectrum of the A 2A’–X 2A’ transition of CaSH has been recorded near 650 nm using laser excitation spectroscopy with selected fluorescence detection. While both a-type and b-type rotational transitions have been observed, extensive measurements have been made for the b-type transitions up to K’a = 4 and K‘a = 5. Altogether over 3000 rotational lines have been measured and fitted with an A-reduced Hamiltonian. The X 2A’ state has rotational constants A=9.693 322(46) cm-1, B=0.141 864 7(33) cm-1, and C=0.139 581 0(33) cm-1. The A 2A’ state has a band origin at 15 380.284 7(2) cm-1, and effective values for the rotational constants A=9.090 808(78) cm-1, B=0.147 459 8(34) cm-1, and C=0.144 804 2(34) cm-1. An approximate r0 structure for CaSH is discussed. The A 2A’ state is the lower energy Renner–Teller component of the ‘‘A 2Π’’ state of the hypothetical linear CaSH molecule, and consequently was found to have a relatively large positive value for the spin–rotation parameter εaa at 3.445 69(26) cm-1. The upper asymmetry component of the F1 spin component of the Ka=1 stack and the F2 spin component of the Ka=0 stack in the A 2A’ state perturb each other with an avoided crossing between J=37.5 and J=38.5. These two spin components interact through the off-diagonal |εab+εba|/2 element of the spin–rotation tensor. For CaSH, the A 2A’ state has |εab+εba|/2=0.065 915(46) cm-1.
ACCESSION #
7618713

 

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