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 Title: Development of a new detection scheme to probe predissociated levels of the S1 state of acetylene Author(s): Jiang, Jun Contributor(s): Field, Robert W.; Merer, Anthony; Erickson, Trevor J. Subject(s): Small molecules Abstract: A new spectroscopic scheme has been developed to probe the predissociated levels of the S$_1$ state of acetylene. Our new scheme is based on detection of visible fluorescence that is a result of multi-photon excitation of acetylene (resonantly through single rovibronic S$_1$ levels). The new detection scheme is not subject to decreases in fluorescence quantum yield of S$_1$ levels that lie above the predissociation limit, and laser scatter-light can be easily eliminated by a long-pass filter with a cutoff in the visible range. For the S$_1$ predissociated levels, the new detection scheme offers much improved signal-to-noise ratio compared to the conventional laser-induced fluorescence technique, based on detection of UV fluorescence from the S$_1$ levels. The new method is also easier to implement than various H-atom detection schemes, which involve one additional laser of different wavelength than the excitation wavelength. Based on the power dependence and lifetime of the fluorescence signals, electronically excited \chem{C_2H} and/or \chem{C_2} fragments are the likely emitters of the detected visible fluorescence. The new method is currently being used to extend the vibrational and rotational assignments of both gerade and ungerade levels of the S$_1$ state of acetylene in the region of the $cis$-$trans$ isomerization barrier, $>$1000 cm$^{-1}$ above the onset of S$_1$ predissociation. Issue Date: 2016-06-22 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper/Presentation Type: Text Language: En URI: http://hdl.handle.net/2142/91305 Rights Information: Copyright 2016 by the authors Date Available in IDEALS: 2016-08-22
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