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 Title: IDENTIFICATION OF PHOTOFRAGMENTS FROM ONE-COLOR RESONANTLY-ENHANCED (̃textA−̃textX) MULTI-PHOTON PHOTODISSOCIATION OF ACETYLENE Author(s): Jiang, Jun Contributor(s): Field, Robert W; Muthike, Angelar K Subject(s): Small molecules Abstract: One-color (212-220 nm) multi-photon photodissociation of acetylene, resonantly enhanced by the $tilde{text{A}}$(S$_1$)$-tilde{text{X}}$ transition, gives rise to strong photofragment fluorescence signals in the visible and near UV regions. In this work, fluorescence signals from the photofragments, generated with three intermediate S$_1$ levels ($trans$ $3^4$, $trans$ $3^5$, and $cis$ $3^16^1$), are studied, both in the flow cell and supersonic jet conditions. In the flow cell ($sim$3 torr), the dispersed fluorescence (DF) spectra of the photofragments are obtained. For all three S$_1$ levels, we observe C$_2$ Swan band ($d^3Pi_g-a^3Pi_u$) and C$_2$ Deslandres-d'Azambuja band ($C^1Pi_g-A^1Pi_u$) emissions, with the former approximately four times more intense than the latter. In the supersonic jet condition (collision-free), fluorescence time-traces at selected wavelength regions are analyzed. We confirm the presence of the two C$_2$ emission bands and their relative intensity observed in the DF spectra. In the supersonic jet condition, we also observe long lifetime visible fluorescence signal ($>$3 $mu$s lifetime), which is likely due to emissions from C$_2$H fragment, based on previous vacuum UV photolysis studies of acetylene. The photodissociation mechanism is inferred, based on our analysis of the flow cell DF spectra and the fluorescence time-traces obtained in the supersonic jet condition. The C$_2$H fragment is likely generated from one-photon photodissociation of S$_1$ acetylene, and an additional photon dissociates the C$_2$H fragment into the C$_2$ $C$ and $d$ states. Issue Date: 6/20/2017 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/97021 DOI: 10.15278/isms.2017.TK05 Date Available in IDEALS: 2017-07-27
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