Showing papers by "Yutaka Matsumi published in 1990"

Formation of O(3Pj) photofragments from the Hartley band photodissociation of ozone at 226 nm

Abstract: The photodissociation of ozone at 226 nm is studied for O3→O2(X3 Σ−g)+O(2p3Pj) by probing O(3Pj) atomic photofragments with a resonance‐enhanced multiphoton ionization method. Angular and kinetic energy distributions are determined by measuring time‐of‐flight spectra as a function of the angle between the polarization vector of the dissociation laser and the detector axis. The Doppler width of O(3Pj) photofragments is also measured. The translational energy distribution is well represented by assuming the formation of vibrationally excited O2 molecules with an average vibrational quantum number of 12. The anisotropy parameter β for the angular distribution is found to be 0.7±0.1. The predissociation dynamics from the photoprepared O3(1B2) state to the repulsive potential surface is discussed.

Photodissociation of hydrogen chloride and hydrogen bromide

Abstract: The Doppler profiles of the hydrogen atom photofragments from the photodissociation of HCl and HBr at 157 and 243 nm are observed to determine the symmetries of the photoexcited states by using a resonance enhanced multiphoton ionization technique. The phototransitions are perpendicular for HCl at 157 nm and 193 nm and for HBr at 157 nm and 243 nm. Isotope effects on the branching ratios of [Cl*(2P1/2)]/[Cl(2P3/2)] are observed for the photodissociation of HCl and DCl at 157 and 193 nm. Our results indicate that in the photodissociation processes of HCl (A 1Π) the dynamical curve crossings during the breakup of the molecule play important roles in the determination of the branching ratio.

Doppler spectroscopy of chlorine atoms generated from photodissociation of hydrogen chloride and methyl chloride at 157 and 193 nm

Abstract: Hydrogen chloride and methyl chloride are photodissociated at 193 and 157 nm. Branching ratios for production of the resulting chlorine atoms in the 2P1/2 state relative to the 2P3/2 state are determined to be 0.20±0.02 at 193 nm and 0.35±0.05 at 157 nm for HCl and 0.23±0.02 at 193 nm and 0.26±0.05 at 157 nm for CH3Cl. The Doppler profiles of the chlorine fragments have been measured and are interpreted by assuming their anisotropy parameters and translational energies. HCl undergoes a perpendicular optical transition at each of the two wavelengths. For CH3Cl, the transition is parallel at 193 nm and a mixture of parallel and perpendicular types at 157 nm.

Fine structure branching ratios of the O(3Pj) atomic fragments from photodissociation of oxygen molecules at 157 and 193 nm

Abstract: Direct photodissociation and predissociation of molecular oxygen from the B 3∑−u state have been studied by photoexcitation at 157 and 193 nm, respectively. The fine structure branching ratios and Doppler profiles of O(3Pj) photofragments were measured by a resonance‐enhanced multiphoton ionization technique. The branching ratios of O(3Pj) j=2,1,0 are 0.74 ±0.03: 0.21 ±0.02: 0.042±0.004 for photodissociation at 157 nm and 0.47±0.05: 0.31 ±0.04: 0.22±0.44 at 193 nm. Both distributions are not statistical. The Doppler profiles of O(3Pj) from photodissociation of O2 at 157 nm are consistent with formation of O(1D)+O(3Pj).

Vacuum ultraviolet photochemistry of CHFCl2 and CHFBr2. Absorption spectra and CHF(Ã 1A″) radical formation

Abstract: Photoabsorption and fluorescence excitation spectra of CHFCl2 and CHFBr2 were measured in the wavelength region 106–200 nm using synchrotron radiation as a light source. The Rydberg excitations of the outer shell orbitals are discussed. The He(i) photoelectron spectrum of CHFBr2 was first measured. Diffuse emission band of CHF(A 1A‘→X 1A’) was observed in the 350–700 nm region, in which the 2n0 (n=0–4) vibrational progression and 201 transition were identified. The CClF(A 1A‘) radical was produced together with CHF(A 1A‘) in the photodecomposition of CHFCl2. The radiative lifetimes of the A 1A‘ states of CHF and CClF were determined to be 2.57±0.16 μs and 644±15 ns, respectively. In the photolysis of CHFCl2 fluorescence starts at 155 nm and shows a maximum quantum yield Φ=0.22 at 107.5 nm, while the CHFBr2 excitation gives a maximum of Φ=0.016 at 117.5 nm.