Probing cis-trans isomerization in the S1 state of C2H2 via H-atom action and hot band-pumped IR-UV double resonance spectroscopies

The Journal of Chemical Physics
P Bryan ChangalaR W Field

Abstract

We report novel experimental strategies that should prove instrumental in extending the vibrational and rotational assignments of the S1 state of acetylene, C2H2, in the region of the cis-trans isomerization barrier. At present, the assignments are essentially complete up to ∼500 cm(-1) below the barrier. Two difficulties arise when the assignments are continued to higher energies. One is that predissociation into C2H + H sets in roughly 1100 cm(-1) below the barrier; the resulting quenching of laser-induced fluorescence (LIF) reduces its value for recording spectra in this region. The other difficulty is that tunneling through the barrier causes a staggering in the K-rotational structure of isomerizing vibrational levels. The assignment of these levels requires data for K values up to at least 3. Given the rotational selection rule K' - ℓ('') = ± 1, such data must be obtained via excited vibrational levels of the ground state with ℓ('') > 0. In this paper, high resolution H-atom resonance-enhanced multiphoton ionization spectra are demonstrated to contain predissociated bands which are almost invisible in LIF spectra, while preliminary data using a hyperthermal pulsed nozzle show that ℓ('') = 2 states can be selectively popula...Continue Reading

References

May 28, 2005·The Journal of Chemical Physics·Bernd SchubertHans Lischka
Aug 14, 2008·The Journal of Chemical Physics·Anthony J MererRobert W Field
Jul 5, 2011·The Journal of Chemical Physics·Anthony J MererRobert W Field
Dec 15, 2015·Science·Joshua H BarabanRobert W Field

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Citations

Feb 2, 2016·The Review of Scientific Instruments·J H BarabanJ W Daily
Sep 8, 2018·Chemphyschem : a European Journal of Chemical Physics and Physical Chemistry·Cherumuttathu H Suresh, Padinjare Veetil Bijina
Jan 24, 2019·Physical Chemistry Chemical Physics : PCCP·Michael N R AshfoldJingsong Zhang
Dec 15, 2015·Science·Joshua H BarabanRobert W Field
Jul 12, 2018·The Journal of Physical Chemistry. a·Kevin M RoenitzSteven T Shipman

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