Showing papers by "Yutaka Matsumi published in 2008"

Approach to thermal equilibrium in atomic collisions.

Abstract: The energy relaxation of fast atoms moving in a thermal bath gas is explored experimentally and theoretically. Two time scales characterize the equilibration, one a short time, in which the isotropic energy distribution profile relaxes to a Maxwellian shape at some intermediate effective temperature, and the second, a longer time in which the relaxation preserves a Maxwellian distribution and its effective temperature decreases continuously to the bath gas temperature. The formation and preservation of a Maxwellian distribution does not depend on the projectile to bath gas atom mass ratio. This two-stage behavior arises due to the dominance of small angle scattering and small energy transfer in the collisions of neutral particles. Measurements of the evolving Doppler profiles of emission from excited initially energetic nitrogen atoms traversing bath gases of helium and argon confirm the theoretical predictions.

Kinetics and Mechanism of the Reaction of Chlorine Atoms with n-Pentanal

Abstract: The kinetics and mechanism of the reaction Cl + CH3(CH2)3CHO was investigated using absolute (PLP−LIF) and relative rate techniques in 8 Torr of argon or 800−950 Torr of N2 at 295 ± 2 K. The absolute rate experiments gave k[Cl+CH3(CH2)3CHO] = (2.31 ± 0.35) × 10-10 in 8 Torr of argon, while relative rate experiments gave k[Cl+CH3(CH2)3CHO] = (2.24 ± 0.20) × 10-10 cm3 molecule-1 s-1 in 800−950 Torr of N2. Additional relative rate experiments gave k[Cl+CH3(CH2)3C(O)Cl] = (8.74 ± 1.38) × 10-11 cm3 molecule-1 s-1 in 700 Torr of N2. Smog chamber Fourier transform infrared (FTIR) techniques indicated that the acyl-forming channel accounts for 42 ± 3% of the reaction. The results are discussed with respect to the literature data and the importance of long range (greater than or equal to two carbon atoms along the aliphatic chain) effects in determining the reactivity of organic molecules toward chlorine atoms.

Atmospheric chemistry of cyclohexanone: UV spectrum and kinetics of reaction with chlorine atoms

Abstract: Absolute and relative rate techniques were used to study the reactivity of Cl atoms with cyclohexanone in 6 Torr of argon or 800 950 Torr of N2 at 295 2 K. The absolute rate experiments gave k(Cl + cyclohexanone) = (1.88 0.38) 10 10, whereas the relative rate experiments gave k(Cl + cyclohexanone) = (1.66 0.26) 10 10 cm3 molecule 1 s 1. Cyclohexanone has a broad UV absorption band with a maximum cross section of (4.0 0.3) 10 20 cm2 molecule 1 near 285 nm. The results are discussed with respect to the literature data.

Single Particle Analysis of Secondary Organic Aerosols Formed from 1,4-Cyclohexadiene Ozonolysis Using a Laser-Ionization Single-Particle Aerosol Mass Spectrometer

Abstract: Real-time analysis of secondary organic aerosol (SOA) particles formed from 1,4-cyclohexadiene (CHD) ozonolysis in a smog chamber was performed using a laser-ionization single-particle aerosol mass...