Satoshi Takao

De-excitation rate constants of He(2 3S) by atoms and molecules as studied by the pulse radiolysis method

Abstract Time-resolved measurement of He (2 3 S) concentration by its optical absorption after electron pulse irradiation of HeN 2 mixtures confirms that the optical emission of N + 2 (B 2 Σ + u → X 2 Σ + g ) is based on the energy transfer (Penning ionization) from He (2 3 S) to N 2 . The addition of other atoms and molecules to HeN 2 mixtures changes the decay rate of the optical emission N + 2 (B 2 Σ + u → X 2 Σ + g ), which is a detector of He (2 3 S), and gives the rate constant of He (2 3 S) de-excitation by various atoms and molecules. Our results are discussed from the viewpoint of a gas-kinetic collision model.

Measurements of de-excitation rate constants of Ne(3P2, 3P0 and 3P1) by N2 and SF6 using a pulse radiolysis method

Abstract The de-excitation rate constants of Ne( 3 P 2 , 3 P 0 and 3 P 1 ) by N 2 and SF 6 were measured using a pulse radiolysis method combined with optical absorption spectroscopy. A new absorption law which relates the relative concentration S of absorbing atoms to the measured transmittance T , i.e. in S = Σ 11 i = 0 a i T i , was used for analyzing the data. The presence of a small amount of SF 6 in the sample gas mixtures permitted removal of some artifacts due to thermal electrons for determining the rate constants.

Phosphorescence of biacetyl sensitized by benzene in gas phase pulse radiolysis

The phophorescence of biacetyl induced by an energy transfer to biacetyl from triplet benzene produced in the pulse radiolysis of benzene-biacetyl mixtures has been studied. The time required to reach the maximum intensity of phosphorescence, tmax, after the electron pulse, varies as a function of biacetyl pressure at constant benzene pressure (40 torr), which gives the lifetime of triplet benzene τ = (6.7 ± 3.2) × 10−6 s and the rate constant of the energy transfer kC6H6*(T1) + biacetyl = (1.6 ± 0.7) × 10−10 cm3 molecule−1 s−1.

The electron scavenging by N2O in the radiolysis of liquid hydrocarbons

Abstract The γ-radiolysis of liquid neopentane and 2,2,4-trimethylpentane has been studied in the presence of low concentrations of N 2 O. The addition of N 2 O to neopentane at the mole fraction 1 × 10 −5 ⩽ N S ⩽1 × 10 −4 gives constant G (N 2 ) = 1·1±0.1 at 293±1 K. At lower concentrations, 1 × 10 −7 ⩽ N S ⩽1 × 10 −5 , G (N 2 ), calculated from the nitrogen formation vs dose, leads to the same value, in good agreement with the free-ion yield resulting from electrical conductivity. In 2,2,4-trimethylpentane, G (N 2 ) decreases gradually with decreasing N 2 O concentrations even for 1 × 10 −5 ⩽ N S ⩽1 × 10 −4 . However, for 1 × 10 −6 ⩽ N S ⩽7 × 10 −6 , G (N 2 ) is found to be constant and equal to 0·33, which also agrees well with the free-ion yield. It may be concluded that G (N 2 ) arises from the complete scavenging of the free electrons at 1 × 10 −7 ⩽ N S ⩽1 × 10 −4 in neopentane, and at 1 × 10 −6 ⩽ N S ⩽7 × 10 −6 in 2,2,4-trimethylpentane, and that, at such low concentrations of N 2 O, one N 2 molecule is produced per electron scavenged by N 2 O. Compared with the result obtained for cyclohexane and n -hexane containing N 2 O, the present results may represent typical features of the electron scavenging process in the γ-radiolysis of liquid hydrocarbons at the lower concentrations of N 2 O.