Minoru Endoh

CS+(B2Σ+−A2Πi) emission produced from dissociative charge-transfer reactions of He+ with CS2 and OCS at thermal energy

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 + (BA) 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 + (BA) transition. The irregularities of the locations and intensities of the CS + (BA) 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.

Thermal energy charge−transfer reactions: He+2 with N2 and CO

The reactions of He+2 with N2 and CO at thermal energy have been studied by optical emission spectroscopy in a He flowing afterglow. The following emission systems have been observed: N+2(B 2Σ+u− X 2Σ+g) and CO+(B 2Σ+−X 2Σ+, B 2Σ+− A 2Πi, A 2Πi−X 2Σ+). The vibrational and rotational distributions of the products have been determined. A Franck–Condon‐like vibrational distribution is obtained for N2+(B) and CO+(B) which are formed through energy‐resonant processes. In contrast, the vibrational distribution of CO+(A), which is formed through a nonenergy‐resonant process, is shifted to higher vibrational levels in comparison with Franck–Condon‐type distribution. Simple model calculations are suggestive of mutual effects of Franck–Condon and energy resonance criteria for the formation of CO+(A) vibrational levels. Rotational excitations are observed in N2+(B) and CO+(B). The effective rotational temperatures of N+2(B: v′=0) and CO+(B: v′=0) are 900±60 and 890±100 K, respectively.

SO+(A2Π-X2Πr) emission produced from a dissociative charge-transfer reaction of He+ with SO2 at thermal energy

Abstract The extensive bands observed from the helium afterglow reaction of SO 2 in the 250–540 nm region are assigned to the new SO + (A 2 Π-X 2 Π r ) system produced from the He + /SO 2 dissociative charge-transfer reaction at thermal energy. They had been erroneously interpreted as the SO + 2 (C-X) system produced from He(2 3 S)/SO 2 Penning ionization. The spectroscopic constants for the SO + A 2 Π) and SO + (X 2 Π r ) states were determined.

CO2+(ÖX̃ and B̃–X̃) emissions resulting from the He(2 3S)+CO2 Penning ionization

CO2+ (A 2Πu–X 2Πg) and CO2+ (B 2Σu+−X 2Πg) emissions produced from the He(2 3S)+CO2 Penning ionization have been observed in a flowing afterglow apparatus. The fluorescence branching ratio of the A 2Πu and B 2Σu+ states, and the vibrational populations of the A state were determined as a function of helium pressure. The fluorescence branching ratio of the A and B states was independent of the helium pressure at 0.5–1.0 Torr. Meanwhile, a significant relaxation was found for the vibrational distribution of the A state in the helium pressure range from 0.5 to 5 Torr. The unrelaxed vibrational distribution of the A state was determined from the 62 A–X bands. The fluorescence branching ratio IA/IB was about four times larger than the initial population ratio of the A and B states determined by electron spectroscopy, and the vibrational populations of the A state shifted to higher υ1′ levels (υ1′= 3,4, and 5). These discrepancies between the PIOS and PIES results have been interpreted as due to interele...

Chemiluminescent reaction at thermal energy: Vibrational distribution of CO+(A 2Π) from the C+ O2 reaction

Abstract CO+(A 2Π-X2Σ+) emission produced from the C+(2P) + O2 reaction has been observed at thermal energy in a flowing afterglow apparatus. The relative vibrational population in the CO+(A 2Π) state was determined. The average fraction of vibrational energy distributed in CO+(A 2Π),(fV,), was estimated to be 0.20 ± 0.02.

CS2+(A-X) emission produced from the charge-transfer reaction of Ar2+ with CS2 in the Ar afterglow

CS2 in an Ar afterglow exhibited emission from the 00 – 11 and 22 levels of CS2+(A2Πu- X2Πg). The excitation source was attributed to Ar2+. The vibrational frequencies of CS2+(X: ν2″ = 4 and ν1″ + 12ν2″ = 3) were determined from the vibrational analysis of the (ν1″,ν2 ″,0) progressions from the 00 level. The relative vibrational population shows a sinificant deviation from a Franck—Condon distribution.

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.

Optical spectroscopic study of thermal‐energy charge transfer between He+ and CO2

The thermal‐energy charge transfer between He+ and CO2 has been studied by optical spectroscopy in a flowing afterglow apparatus fitted with pulse modulation equipment. CO+ (A 2Π–X 2Σ+) emission from v′(vi:)=0 to v′(vi:)=11 has been identified in the 300–500 nm region. The excitation rate constant of CO+ (A) was evaluated by comparing the total emission intensity with that for N+2 (B−X) emission in He+/N2. The upper limit to the excitation rate constant for CO+ (A) represents only 1% of all CO+ produced in the He+/CO2 reaction. The CO+(A) vibrational population was approximately exponential corresponding to an effective vibrational temperature of 10 500±900 K. The long range resonant model for the He+/CO2 reaction is discussed in the light of recent information on the product distribution and the excited states of CO+2.

Optical study of the He2+ + CO2 charge-transfer reaction at thermal energy

Abstract The CO 2 + (A 2 Π u -X 2 Π g , B 2 Σ u + -X 2 Π g ) emission spectra resulting from the thermal energy He 2 + + CO 2 reaction have been recorded in a He flowing afterglow. The rate constants for A and B production and vibrational populations of the A state were determined and compared with those in He(2 3 S) Penning ionization and HeI photoionization. The rate constants for Ā and B production were larger than those in He(2 3 S) Penning ionization. The initial electronic state population ratio Ā/B, calculated by taking account of the fraction of conversion from the B to A state, was smaller than those in He(2 3 S) Penning ionization and HeI photoionization. It was concluded that two types of charge-transfer processes occur in the thermal energy He 2 + + CO 2 reaction: (1) energy resonant process leading to CO 2 + (C) and (2) non-energy resonant process leading to CO 2 + (B, A). The CO 2 + (A) vibrational distribution was found to shift to high vibrational levels relative to those in He(2 3 S) Penning ionization and HeI photoionization. The CO 2 + (A) vibrational excitation was interpreted as due to the energy-resonance requirement and interelectronic state coupling between the B and A states.