Photofragment translational spectroscopy of CH2I2 at 304 nm: Polarization dependence and energy partitioning

TitlePhotofragment translational spectroscopy of CH2I2 at 304 nm: Polarization dependence and energy partitioning
Publication TypeJournal Article
Year of Publication1997
AuthorsJung, K-W, Ahmadi, TS, EL-Sayed, MA
JournalBulletin of the Korean Chemical Society
Date PublishedDec
ISBN Number0253-2964
Accession NumberWOS:000071415300015

The photodissociation dynamics of CH2I2 has been studied at 304 nm by state-selective photofragment translational spectroscopy. Velocity distributions, anisotropy parameters, and relative quantum yields are obtained for the ground I(P-2(3/2)) and spin-orbit excited state I*(P-2(1/2)) iodine atoms, which are produced from photodissociation of CH2I2 at this wavelength. These processes are found to occur via B-1 <-- A(1) type electronic transitions. The quantum yield of I*(P-2(1/2)) is determined to be 0.25, indicating that the formation of ground state iodine is clearly the favored dissociation channel in the 304 nm wavelength region. From the angular distribution of dissociation products, the anisotropy parameters are determined to be beta(I)=0.4 for the I(P-2(3/2)) and beta (I*)=0.55 for the I*(P-2(1/2)) which substantially differ from the limiting value of 1.13. The positive values of anisotropy parameter, however, show that the primary processes for I and I* formation channels proceed dominantly via a transition which is parallel to I-I axis. The above results are interpreted in terms of dual path formation of iodine atoms from two different excited states, i.e., a direct and an indirect dissociation via curve crossing between these states. The translational energy distributions of recoil fragments reveal that a large fraction of the available energy goes into the internal excitation of the CH2I photofragment; /E-avl=0.80 and 0.82 for the I and I* formation channels, respectively. The quantitative analysis for the energy partitioning of available energy into the photofragments is used to compare the experimental results with the prediction of direct impulsive model for photodissociation dynamics.