Ra. Brownsword et al., QUANTUM YIELD FOR H ATOM FORMATION IN THE METHANE DISSOCIATION AFTER PHOTOEXCITATION AT THE LYMAN-ALPHA (121.6 NM) WAVELENGTH, Chemical physics letters, 266(1-2), 1997, pp. 259-266
The gas-phase photodissociation dynamics of methane after excitation a
t the Lyman-alpha wavelength (121.6 nm) was investigated under collisi
on-free conditions at room temperature. Narrow-band tunable Lyman-cr l
aser radiation was generated by the resonant third-order sum-differenc
e frequency conversion of pulsed-dye laser radiation and used both to
photodissociate the parent molecules and to detect the photolytically
produced hydrogen atoms via (2p(2)P<--1s(2)S) laser-induced fluorescen
ce. H atom Doppler profiles were recorded and the absolute quantum yie
ld for H atom formation, Phi(H) = (0.47 +/- 0.11), was determined by m
eans of a photolytic calibration method where the Lyman-alpha photolys
is of H2O was used as a reference source of well-defined H atom concen
trations, This value will be used in combination with previous results
from H-2 and CH yield measurements to estimate the relative importanc
e of the different product pathways in the CH4 photodissociation.