R2PI detection of the quantum yields of I(2P1/2) and I(2P3/2) in the photodissociation of C2F5I, n-C3F7I, i-C3F7I and CH3I

Resonant two-photon ionization R2PI has been applied to the measurements of the quantum yields phi of iodine atoms in the fine structure states (2)p(1/2) and P-2(3/2) arising in the UV-photodissociation process (lambda = 266 and 355 nm) of the perfluoroalkyliodides C2F5I, n-C3F7I and i-C3F7I as well as of methyl iodide CH3I (lambda = 265 nm). The measured values of the quantum yields of the excited state ( P-2(1/2)) of the I atoms are found to be phi(266)* = 0.921 +/- 0.010 and phi*(266) = 0.178 +/- 0.025 for C2F5I, phi*(266) = 0.919 +/- 0.011 and phi(355)*= 0.296 +/- 0.029 for n-C3F7I, phi(266)* = 0.900 +/- 0.015 and phi(266)* = 0.396 +/- 0.034 for i-C3F7I, and phi*(266) = 0.71 +/- 0.03 for CH3I. The results obtained show that the quantum yield phi*(266) Of the excited state atoms I(P-2(1/2)) in the photodissociation process of the perfluoroalkyliodides differs noticeably from unity which has previously been assumed or measured for these molecules. (C) 2000 Elsevier Science B.V. All rights reserved.