Triply differential photoelectron studies of non-Franck–Condon behavior in the photoionization of acetylene

Journal Article · Fri Jan 01 04:00:00 EST 1982 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.443568· OSTI ID:5456157

Parr, Albert C. ^[1]; Ederer, D. L. ^[1]; West, J. B. ^[2]; Holland, D. M. P. ^[3]; Dehmer, Joseph L. ^[4]

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1. National Bureau of Standards, Washingtion D.C., (United States)
2. Daresbury Lab. (United Kingdom). Cockcroft Inst. of Accelerator Science and Technology (AST)
3. Univ. of Maryland, College Park, MD (United States)
4. Argonne National Lab. (ANL), Argonne, IL (United States)

Vibrational branching ratios and photoelectron angular distributions for alternative vibrational levels of C₂H⁺₂ X² Π_u have been measured in the range 13 eV≤hv≤25 eV using synchrotron radiation. Below hv≈16 eV, these data exhibit strong non-Franck--Condon effects, namely, wavelength-dependent vibrational branching ratios and vibrational-state-dependent photoelectron asymmetry parameters. Moreover, enhanced excitation of bending modes of the ion is observed below hv≈16 eV, in addition to the C--C stretch mode, which is the only mode readily observed in photoelectron spectra of C₂H₂ at shorter wavelengths, e.g., at the He I (21.2 eV) resonance line. The non-Franck--Condon behavior is attributed to resonant photoionization processes, whose identification is discussed in the framework of several recent theoretical and experimental studies on acetylene and related molecules.

• Research Organization: Synchrotron Ultraviolet Radiation Facility, National Bureau of Standards, Washington, D.C. 20234
• Sponsoring Organization: USDOE; Office of Naval Research (ONR)
• OSTI ID: 5456157
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 9 Vol. 76; ISSN JCPSA6; ISSN 0021-9606
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400104* -- Spectral Procedures-- (-1987)
ACETYLENE
ALKYNES
ANGULAR DISTRIBUTION
BREMSSTRAHLUNG
DISTRIBUTION
ELECTROMAGNETIC RADIATION
ELECTRON SPECTROSCOPY
ENERGY LEVELS
ENERGY RANGE
EV RANGE
EV RANGE 10-100
EXCITED STATES
FRANCK-CONDON PRINCIPLE
HYDROCARBONS
IONIZATION
ORGANIC COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PHOTOIONIZATION
RADIATIONS
RESONANCE
SPECTROSCOPY
SYNCHROTRON RADIATION
VIBRATIONAL STATES