Generation and detection of alkyl peroxy radicals in a supersonic jet expansion

Journal Article · Fri Jul 07 04:00:00 EDT 2006 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.2209680· OSTI ID:20864265

Fu, H B; Hu, Y J; Bernstein, E R ^[1]

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1. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872 (United States)

Alkyl peroxy radicals are synthesized in a supersonic jet expansion by the initial production of alkyl radicals and subsequent reaction with molecular oxygen. Parent ions CH{sub 3}OO{sup +}/CD{sub 3}OO{sup +} are observed employing vacuum ultraviolet (VUV) single photon ionization/time-of-flight mass spectroscopy (TOFMS). Employing infrared (IR)+VUV photofragmentation detected spectroscopy, rotationally resolved infrared spectra of jet-cooled CH{sub 3}OO and CD{sub 3}OO radicals are recorded for the A-tilde{sup 2}A{sup '}<-X-tilde{sup 2}A{sup ''} transition by scanning the IR laser frequency while monitoring the CH{sub 3}{sup +} and CD{sub 3}{sup +} ion signals generated by the VUV laser. The band origins of the A-tilde{sup 2}A{sup '}<-X-tilde{sup 2}A{sup ''} transition for CH{sub 3}OO and CD{sub 3}OO are identified at 7381 and 7371 cm{sup -1}, respectively. Rotational simulation for the CH{sub 3}OO and CD{sub 3}OO 0{sub 0}{sup 0} transitions of A-tilde<-X-tilde yields a rotational temperature for these radicals of {approx}30 K. With the aid of ab initio calculations, two and five vibrational modes for the A-tilde{sup 2}A{sup '} excited electronic state are assigned for CH{sub 3}OO and CD{sub 3}OO radicals, respectively. Both experimental and theoretical results suggest that the ground electronic state of the ions of ethyl and propyl peroxy radicals are not stable although their ionization energies (IE) are less than 10.5 eV. The C{sub 2}H{sub 5}OO{sup +}/C{sub 3}H{sub 7}OO{sup +} cations can readily decompose to C{sub 2}H{sub 5}{sup +}/C{sub 3}H{sub 7}{sup +} and O{sub 2}. This is partially responsible for the inability of IR+VUV photofragmentation spectroscopy to detect the near IR A-tilde<-X-tilde electronic transition for these radicals.

• OSTI ID: 20864265
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 125; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALKYL RADICALS
CATIONS
DETECTION
EV RANGE 10-100
FAR ULTRAVIOLET RADIATION
INFRARED SPECTRA
IONIZATION POTENTIAL
MASS SPECTRA
MASS SPECTROSCOPY
OXYGEN
PEROXY RADICALS
PHOTOIONIZATION
PHOTOLYSIS
REACTION KINETICS
ROTATIONAL STATES
TIME-OF-FLIGHT METHOD
ULTRAVIOLET SPECTRA
VIBRATIONAL STATES