science-softCon uv/vis spectra data base;		www.uv-spectra.de; (C) science-softCon 2008

Substance:	methyl radical			Other Names: 

Formula:  	CH3				CAS-No.: 2229-07-4

Study: absorption, quantum yields

                
Authors: V. Khamaganov, R. Karunanandan, A. Rodriguez, J. N. Crowley

Title: Photolysis of CH3C(O)CH3 (248 nm, 266 nm), CH3C(O)C2H5 (248 nm) and CH3C(O)Br (248 nm): pressure 
dependent quantum yields of CH3 formation

Journal/Source: Phys. Chem. Chem. Phys., 9, 4098 - 4113, (2007); DOI: 10.1039/b701382e


Data: (diagram, table, disk):

Wavelength range: 216.4 nm

Resolution: 0.5 nm

Temperature: 298 K

Temperature dependence: 

Pressure: 5 - 1500 Torr (N2)


Comments: he formation of CH3 in the 248 or 266 nm photolysis of acetone (CH3C(O)CH3), 2-butanone (methylethylketone, MEK, CH3C(O)C2H5) 
and acetyl bromide (CH3C(O)Br) was examined using the pulsed photolytic generation of the radical and its detection by transient absorption 
spectroscopy at 216.4 nm.
For acetone at 248 nm, the yield of CH3 was greater than unity at low pressures (1.42 ± 0.15 extrapolated to zero pressure).
At 266 nm, the yields of CH3 (and CH3CO) were close to unity (0.93 ± 0.1) and independent of pressure.
As part of this study, the absorption cross section of CH3 at 216.4 nm (instrumental resolution of 0.5 nm) was measured to 
be (4.27 ± 0.2) × 10-17 cm2 molecule-1 and that of C2H5 at 222 nm was (2.5 ± 0.6) × 10-18 cm2 molecule-1. An absorption 
spectrum of gas-phase CH3C(O)Br (210-305 nm) is also reported for the first time.

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