Absolute Photoionization Cross Section of the Ethyl Radical in the Range 8-11.5 eV: Synchrotron and Vacuum Ultraviolet Laser Measurements

作者：Gans Berenger; Garcia Gustavo A; Boye Peronne Severine; Loison Jean Christophe^*; Douin Stephane; Gaie Levrel Francois; Gauyacq Dolores

来源：Journal of Physical Chemistry A, 2011, 115(21): 5387-5396.

DOI：10.1021/jp202648m

The absolute photoionization cross section of C(2)H(5) has been measured at 10.54 eV using vacuum ultraviolet (VUV) laser photoionization. The C(2)H(5) radical was produced in situ using the rapid C(2)H(6) + F -> C(2)H(5) + HF reaction. Its absolute photoionization cross section has been determined in two different ways: first using the C(2)H(5) + NO(2) -> C(2)H(5)O + NO reaction in a fast flow reactor, and the known absolute photoionization cross section of NO. In a second experiment, it has been measured relative to the known absolute photoionization cross section of CH(3) as a reference by using the CH(4) + F -> CH(3) + HF and C(2)H(6) + F -> C(2)H(5) + HF reactions successively. Both methods gave similar results, the second one being more precise and yielding the value: sigma(ion)(C1HS) = (5.6 +/- 1.4) Mb at 10.54 eV. This value is used to calibrate on an absolute scale the photoionization curve of C(2)H(5) produced in a pyrolytic source from the C(2)H(5)NO(2) precursor, and ionized by the VUV beam of the DESIRS beamline at SOLEIL synchrotron facility. In this latter experiment, a recently developed ion imaging technique is used to discriminate the direct photoionization process from dissociative ionization contributions to the C(2)H(5)(+) signal. The imaging technique applied on the photoelectron signal also allows a slow photoelectron spectrum with a 40 meV resolution to be extracted, indicating that photoionization around the adiabatic ionization threshold involves a complex vibrational overlap between the neutral and cationic ground states, as was previously observed in the literature. Comparison with earlier photoionization studies, in particular with the photoionization yield recorded by Ruscic et al.(1) is also discussed.

• 出版日期2011-6-2