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

Journal Article · · Journal of Chemical Physics
DOI:https://doi.org/10.1063/1.4929588· OSTI ID:1547032
 [1];  [2];  [3];  [4]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Colorado, Boulder, CO (United States); Office of Scientific and Technical Information (OSTI)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Colorado, Boulder, CO (United States)
  3. Academia Sinica, Taipei (Taiwan); Univ. of British Columbia, Vancouver, BC (Canada)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
+ Show Author Affiliations
We observe 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 issues 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 populated in a jet, giving access to K' = 3 states in IR-UV double resonance.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
Academia Sinica; Natural Sciences and Engineering Research Council of Canada; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
FG02-87ER13671
OSTI ID:
1547032
Alternate ID(s):
OSTI ID: 1831805
OSTI ID: 1229645
OSTI ID: 22493579
Journal Information:
Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 8 Vol. 143; ISSN JCPSA6; ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (4)

Hidden Dicarbene Nature of Acetylenes and Captodative Bonding on Carbon journal October 2018
Photoinduced C–H bond fission in prototypical organic molecules and radicals journal January 2019
Probing the predissociated levels of the S 1 state of acetylene via H-atom fluorescence and photofragment fluorescence action spectroscopy journal November 2018
One-colour (∼220 nm) resonance-enhanced (S 1  − S 0 ) multi-photon dissociation of acetylene: probe of the C 2 A 1 Π u  −  X 1 Σ + g band by frequency-modulation spectroscopy journal February 2020

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