@article {2623,
	title = {Stretch-bend combination polyads in the (A)over-tilde(1)A(u) state of acetylene, C2H2},
	journal = {Journal of Molecular Spectroscopy},
	volume = {256},
	number = {2},
	year = {2009},
	note = {ISI Document Delivery No.: 478PDTimes Cited: 0Cited Reference Count: 55Steeves, Adam H. Bechtel, Hans A. Merer, Anthony J. Yamakita, Nami Tsuchiya, Soji Field, Robert W.},
	month = {Aug},
	pages = {256-278},
	type = {Article},
	abstract = {Rotational analyses are reported for a number of newly-discovered vibrational levels of the SI-trans; ((A) over tilde (1)A(u)) state of C2H2. These levels are combinations where the Franck-Condon active nu(2){\textquoteright} and nu(3){\textquoteright} vibrational modes are excited together with the low-lying bending vibrations, nu(4){\textquoteright} and nu(6){\textquoteright}. The structures of the bands are complicated by strong a- and b-axis Coriolis coupling, as well as Darling-Dennison resonance for those bands that involve overtones of the bending vibrations. The most interesting result is the strong anharmonicity in the combinations of nu(3){\textquoteright} (trans bend, a(g)) and nu(6){\textquoteright} (in-plane cis bend, b(u)). This anharmonicity presumably represents the approach of the molecule to the trans-cis isomerization barrier, where ab initio results have predicted the transition state to be half-linear, corresponding to simultaneous excitation of nu(3){\textquoteright} and nu(6){\textquoteright}. The anharmonicity also causes difficulty in the least squares fitting of some of the polyads, because the simple model of Coriolis coupling and Darling-Dennison resonance starts to break down. The effective Darling-Dennison parameter, K-4466, is found to increase rapidly with excitation of nu(3){\textquoteright}, while many small centrifugal distortion terms have had to be included in the least squares fits in order to reproduce the rotational structure correctly. Fermi resonances become important where the K-structures of different polyads overlap, as happens with the 2(1)3(1)B(1) and 3(1)B(3) polyads (B = 4 or 6). The aim of this work is to establish the detailed vibrational level structure of the S-1-trans state in order to search for possible S-1-cis ((1)A(2)) levels. This work, along with results from other workers, identifies at least one K sub-level of every single vibrational level expected up to a vibrational energy of 3500 cm(-1). (C) 2009 Elsevier Inc. All rights reserved.},
	keywords = {1AU, AB-INITIO MO, acetylene, Cis-trans isomerization, DISPERSED, DOUBLE-RESONANCE SPECTROSCOPY, FLUORESCENCE, FLUORESCENCE-SPECTRUM, INTRAMOLECULAR VIBRATIONAL REDISTRIBUTION, LASER-INDUCED, PARTIAL DEPERTURBATION, POLYATOMIC-MOLECULES, ROTATION CONSTANTS, STATE, vibration-rotation analysis, X BAND SYSTEM},
	isbn = {0022-2852},
	url = {<Go to ISI>://000268599300013},
	author = {Steeves, A. H. and Bechtel, H. A. and Merer, A. J. and Yamakita, N. and Tsuchiya, S. and Field, R. W.}
}
