Kazunari Kobarai

Formation of CH(A2Δ,B2Σ-,C2Σ+) by electron-ion recombination processes in the argon and krypton afterglow reactions of CH4

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...

Dissociative excitation of CH4 by collisions with helium active species

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).

Dissociative excitation of SiH4 by collisions with metastable argon atoms

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.

Dissociative excitation of GeH4 by collisions with Ar and He active species

The product channels in reactions of metastable Ar(3P2) and He(23S) atoms and Ar+, (Ar+)*, He+, and He+2 ions with GeH4 have been studied by observing emission spectra in the flowing afterglow and beam apparatus. H*, Ge*, GeH(A 2Δ–X 2Π), and GeH+(a 3Π0+,1–X 1Σ+) emissions were observed in the 190–600 nm region. The effect of SF6 addition into the discharge flow indicated that secondary electron‐ion recombination processes participate in the formation of Ge* and GeH(A) in the Ar and He afterglows. The formation of Ge* through the Ar+/GeH4 reaction followed by electron‐ion recombination processes was confirmed by simultaneous formation of Ar+ and low‐energy electrons through the He(2 3S)/Ar Penning ionization. The total emission rate constants were determined to be 8.6 and 0.15×10−12 cm3 s−1 for Ge* and GeH(A) in the Ar(3P2)/GeH4 reaction, and 0.068 and 5.8×10−12 cm3 s−1 and for H* and Ge* in the He(2 3S)/GeH4 reaction, respectively.

Dissociative excitation of SiH4 by collisions with helium active species

Abstract Dissociative excitation of SiH 4 by collisions with metastable He(2 3 S) atoms and He + and/or He 2 + ions has been spectroscopically studied by using flowing afterglow and beam apparatus. The total emission rate constant of Si* produced from the He (2 3 S)/ SiH 4 reaction was determined to be (1.1±0.1) × 10 −12 cm 3 s −1 . A new broad band, which may originate from either SiH x * o SiH x + * ( x =2, 3), was found in the 300–350 nm region.

Nascent rovibrational distribution of O+2(A 2Πu) produced by He(2 3S) Penning ionization of O2

The He(2 3S) Penning ionization of O2 to give O+2(A 2Πu) has been studied by observing the O+2(A 2Πu–X 2Πg) emission in beam and flowing afterglow apparatus. A comparison of beam and flowing afterglow data indicates that the nascent rovibrational distribution is lost in the flowing afterglow due to collisional relaxation. The nascent vibrational distribution of O+2(A 2Πu) shifts to lower vibrational levels in comparison with the Franck–Condon factors for vertical O2(X)→O+2(A) ionization. The rotational temperature decreases from 4200 K for v’=0 to 400 K for v’=13. Vibrational relaxation of O+2(A) accompanied by a significant rotational excitation is explained as a result of a short‐range repulsive interaction [He–O+2(A)→He+O+2(A)] in the exit channel.

Dissociative excitation of SiH4 by collisions with krypton active species

Abstract The dissociative excitation of SiH 4 by collisions with metastable Kr( 3 P 2 ) atoms and (Kr + ) * ions has been studied using flowing afterglow and beam apparatus. The emission rate constants of SiH(A 2 Δ) and Si * produced from the Kr( 3 P 2 )/SiH 4 reaction were determined to be (1.0±0.3)×10 −11 and (0.0069±0.0021)×10 −11 cm 3 s −1 , respectively. The nascent rovibrational distribution of SiH(A) was estimated from a spectral simulation: N 0 : N 1 : N 2 = 100 ( T 0 = 1400 K):40 ( T 1 = 1100 K):5 ( T 2 = 800 K). When (Kr + ) * ions were involved in the discharge flow, strong Si * lines resulting from electron-ion recombination processes were observed.

Dissociative Excitation of GeH4 by Collisions with Krypton Active Species in the Flowing Afterglow

The dissociative excitation of GeH4 by collisions with metastable Kr(3P2) atoms and Kr+ and (Kr+)* ions has been investigated in a flowing-afterglow reactor at 300 K. Ge* and GeH(A-X) emissions were observed in the 190-410-nm region. The total emission rate constants of Ge* and GeH(A2Δ) produced from the Kr(3P2)/GeH4 reaction were determined to be (2.6±0.3) and (0.71±0.07)×10-13 cm3s-1, respectively. When Kr+ and (Kr+)* ions were involved in the discharge flow, Ge* and GeH(A-X) emissions resulting from the primary (Kr+)*/GeH4 reaction and the secondary electron-ion recombination processes were observed. The rotational distribution of GeH(A) in the Kr(3P2)/GeH4 reaction was estimated from a spectral simulation.