Hiroshi Obase
Kyushu University
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Chemical Physics | 1980
Masaharu Tsuji; Hiroshi Obase; Mamoru Matsuo; Minoru Endoh; Yukio Nishimura
Abstract The Δυ = −1, 0 and 1 sequences of the CS + (B 2 Σ + − A 2 Π i ) system have been identified in the flowing helium afterglow reactions of CS 2 and OCS around 4000 A. The disappearance of the CS + (BA) band when He + was eliminated from the helium flow indicated that CS + (B) was formed by dissociative charge-transfer reactions of He + with CS 2 and OCS at thermal energy. The vibrational analysis provided estimates for the vibrational constants of the CS + (B) state, ω e = 911 ± 3 cm −1 and ω e x e = 6.5 ± 1.0 cm −1 . These constants have been used to calculate Morse potential Franck—Condon factors of the CS + (BA) transition. The irregularities of the locations and intensities of the CS + (BA) system from the υ′ = 3 and 4 levels were interpreted as the consequences of perturbations. A weak new CS + (B 2 Σ + −X 2 Σ + ) system produced through the He + /CS 2 reaction was detected in the UV spectral range.
Journal of Chemical Physics | 1980
Masaharu Tsuji; Hiroshi Obase; Yukio Nishimura
Emission spectrum resulting from the energy transfer reaction of He (2 3S) with transient CS radical produced through a microwave discharge of Ar/CS2 mixture was observed in a flowing afterglow apparatus. A new CS+ (B 2Σ+–X 2Σ+) band system due to He (2 3S)/CS Penning ionization was identified in the 220–340 nm region. The dominant bands were the (ν′,0) and (0, ν″) progressions, which was consistent with the prediction from calculated Morse potential Franck–Condon factors. Although the observed bandhead wavelengths of the major CS+ (B–X) emission were in good agreement with those predicted from the reported spectroscopic data, the (4,0) band was located at an abnormal position. It was interpreted as a consequence of vibrational perturbation in the B 2Σ+ state. The relative intensities of CS+(B–X), CS+(B–A), CI, and SI emission were estimated to represent that the dominant pathway of the He (2 3S)/CS reaction is Penning ionization.
Journal of Chemical Physics | 1991
Masaharu Tsuji; Kazunari Kobarai; Hiroyuki Kouno; Hiroshi Obase; Yukio Nishimura
The CH(A–X,B–X,C–X) emission systems have been observed from the Ar and Kr afterglow reactions of CH4. A significant attenuation of the CH(A–X,B–X,C–X) emissions by an addition of SF6 into the discharge flow suggested that the CH(A,B,C) radicals are excited via secondary electron–ion recombination processes. Since the CH(A–X,B–X,C–X) emissions disappeared by trapping ionic active species in the discharge flow, the responsible active species for the CH(A,B,C) production were found to be Ar+ and/or (Ar+)* in the Ar flow and Kr+ and/or (Kr+)* in the Kr flow. The contribution of Ar+ and Kr+ was examined in the He afterglow, where Ar+ or Kr+ and slow electrons were simultaneously produced by the He(23S)/Ar,Kr Penning ionization. Although intense CH(A–X,B–X,C–X) emissions were observed from Ar+/CH4 where CH+n(n=2–4) were formed, they were absent from Kr+/CH4 where only CH+4 was produced. It was, therefore, concluded that CH+2 and/or CH+3 are important precursor ions for the CH(A,B,C) production. The intensity d...
Journal of Chemical Physics | 1991
Masaharu Tsuji; Kazunari Kobarai; Hiroshi Obase; Hiroyuki Kouno; Yukio Nishimura
Dissociative excitation of CH4 by collisions with He(2 3S), He+, and He+2 has been studied by observing CH(A 2Δ–X 2Πr, B 2Σ−–X 2Πr, and C 2Σ+–X 2Πr) and H (Balmer) emissions in the flowing afterglow and beam apparatus. The effect of SF6 addition into the He afterglow indicated that the formation of CH(A,B,C) in the flowing afterglow proceeds through both the primary He(2 3S)/CH4 reaction and a secondary electron–ion recombination reaction through the He+/CH4 and/or He+2/CH4 reactions. The emission rate constants of A–X, B–X, and C–X of CH, Hα, and Hβ produced from the He(2 3S)/CH4 reaction were determined to be 5.6, 1.5, 0.011, 0.46, and 0.072×10−13 cm3 s−1 in the beam experiment, respectively. The nascent vibrational distribution of CH(A) from He(2 3S)/CH4 was determined as N0:N1=100:37±5. The rotational distributions were expressed by single Boltzmann temperatures of 3200±200 and 2600±300 K for v’=0,1 of CH(A) and 3300±200 K for v’=0 of CH(B).
Chemical Physics Letters | 1989
Masaharu Tsuji; Kazunari Kobarai; Sumio Yamaguchi; Hiroshi Obase; Kazuo Yamaguchi; Yukio Nishimura
Abstract The excitation transfer from Ar* to SiH 4 has been studied by observing UV and visible emission in a flowing afterglow and beam apparatus. The emission rates of Sill (A 2 Δ) and Si* atoms have been determined. From the nascent rovibrational distribution of SiH(A), the fractions of the available energy deposited into vibration and rotation of SiH(A) were estimated to be 2.9% and 4.4%, respectively.
Journal of Chemical Physics | 1987
Hiroshi Obase; Masaharu Tsuji; Yukio Nishimura
He(2 3S) Penning ionization of HCl and HBr leading to HCl+(A) and HBr+(A) has been investigated spectroscopically by using a low‐pressure experimental apparatus coupled with a flowing afterglow source. The vibrational distribution of HCl+(A) agrees well with the result obtained by Penning ionization electron spectroscopy (PIES), which shows a Franck–Condon like distribution. In contrast, the vibrational distribution of HBr+(A) is more deexcited than the PIES one shifting to lower vibrational levels relative to Franck–Condon factors for ionization. These findings indicate that the collisional perturbation occurs only at the entrance channel for the He(2 3S)/HCl system, while at both entrance and exit ones for the He(2 3S)/HBr system. The rotational temperature of HCl+(A) decreases from 600±100 K for v′=0 to 300±100 K for v′=5, while that of HBr+(A) is 450±50 K for v′=0 and 400±50 K for v′=1.
Chemical Physics Letters | 1988
Masaharu Tsuji; John P. Maier; Hiroshi Obase; Yukio Nishimura
Abstract Penning ionization of He (2 3 S) + H 2 O and D 2 O has been studied by observing the A 2 A 1 -X 2 B 1 emission system of H 2 O + and D 2 O + in a low-pressure flowing afterglow. The vibrational distributions of H 2 O + (A) and D 2 O + (A) were consistent with those predicted from Franck-Condon-type vertical excitation. A strong underlying continuum, probably due to high rotational excitation, was found in both spectra.
Journal of Chemical Physics | 1987
Sumio Yamaguchi; Masaharu Tsuji; Hiroshi Obase; Hiroshi Sekiya; Yukio Nishimura
A flowing afterglow reactor has been coupled to a low‐pressure chamber for an optical spectroscopic study of the charge–transfer reaction of He+ with SiH4 at thermal energy. The SiH+(A 1Π–X 1Σ+) emission was observed in the 380–610 nm region. The nascent vibrational and rotational distributions of SiH+(A) have been determined. The vibrational distribution for 0≤v’≤3 was approximately exponential with an effective vibrational temperature of 820±60 K. The rotational temperature decreased from 600 K for v’=0 to 300 K for v’=3. These data indicated that only about 3% of the excess energy is released as internal energy of SiH+(A). From the emission rate constant, SiH+(A) represents about 25% of the total SiH+ ion in the He++SiH4 reaction.
Chemical Physics Letters | 1987
Masaharu Tsuji; John P. Maier; Hiroshi Obase; Hiroshi Sekiya; Yukio Nishmura
The OCS+(A2ΠΩ-X2ΠΩ:Ω = 12, 32) emission resulting from the Ar+(2P32) + OCS charge-transfer reaction has been reexamined in a low-pressure flowing afterglow. The fluorescence channel in the the O0 level was found to be open for rotationally excited levels up to J≈ 170 (≈ 5500 cm−1). The rotational distribution of OCS+(A2ΠΩ: O0) could be characterized by a Boltzmann temperature of 4300±500 K for the Ω = 32 component, indicating that 55 ±7% of the excess energy is deposited into the rotation.
Chemical Physics | 1981
Hiroshi Obase; Masaharu Tsuji; Yukio Nishimura
Abstract Energy transfer processes between He(2 3 S) and Ne( 3 P 0.2 ) metastable atoms and CS radicals have been investigated by UV-visible emission spectroscopy. Two exit channels have been identified, Penning ionization leading to CS + ions and dissociative excitation transfer leading to C and S atoms. In both reactions of He(2 3 S) and Ne( 3 P 0.2 ) with CS radicals, Penning ionization was the prominent exit channel, while dissociative excitation transfer was the minor competitive exit channel. Relative vibrational populations of the CS + (B: υ′= 0–6) state were determined from both CS + (B 2 Σ + -A 2 Π) and CS + (B 2 Σ + -X 2 Σ + ) emissions. The vibrational populations have given a strong preference for the lowest vibrational level, particularly in the case of Ne( 3 P 0.2 ), in comparison with the calculated Franck-Condon factors (FCF) for the CS(X) → CS + (B) vertical ionization. The deviation from FCF was discussed in terms of interactions occurring before and after ionization.