Takashi Imajo

The application of a VUV Fourier transform spectrometer and synchrotron radiation source to measurements of: II. The δ(1,0) band of NO

Line-by-line photoabsorption cross-sections of the NO δ(1,0) band were measured with the VUV Fourier transform spectrometer from Imperial College, London, using synchrotron radiation at Photon Factory, KEK, Japan, as a continuum light source. The analysis of the NO δ(1,0) band provides accurate rotational line positions and term values as well as the photoabsorption cross-sections. The molecular constants of the C(1) 2Π level are found to be T0=54 690.155±0.03 cm−1, Bv=1.944 06±0.000 62 cm−1, Dv=(5.91±0.42)×10−5 cm−1, AD=−0.0187±0.0050 cm−1, p=−0.0189±0.0037 cm−1, and q=−0.015 21±0.000 20 cm−1. The sum of the line strengths for all rotational transitions of the NO δ(1,0) band is determined as 4.80×10−15 cm2 cm−1, corresponding to a band oscillator strength of 0.0054±0.0003.

Infrared diode laser spectroscopic detection of the propargyl radical produced in a supersonic jet expansion by UV laser photolysis

Abstract The propargyl radical (CH 2 CCH) was produced in a pulsed supersonic jet expansion by the 193 nm excimer laser photolysis of propargyl chloride, and detected by the method of time-resolved infrared diode laser spectroscopy. A rotational temperature of 16 ± 4 K was obtained in an experiment in which the τ Q 0 -branch lines of the v 6 band were observed. The characteristic behavior of the propargyl radical in a supersonic beam produced by circular and slit nozzles was discussed.

New discharge modulation technique for detection of transient species produced in pulsed supersonic jet by color center laser spectroscopy

Abstract A new discharge modulation technique has been applied to color center laser spectroscopy for the detection of radical species generated in a pulsed supersonic jet. Transition in the ν 3 band of the CH 3 radical rotationally cooled to 23 K were recorded by the phase sensitive detection technique with an improved signal-to-noise ratio. The sensitivity attained corresponds to 6 × 10 −5 absorption.

Collisional quenching of the CO+ A 2Π(ν=1) state by He, Ne, Ar, N2, and CO

Abstract Collisional deactivation processes of the CO + A 2 Π(ν=1) state are investigated by a time-resolved laser-induced fluorescence technique. The overall quenching rate constants are determined to be (9.1±1.0) × 10 −13 , (1.3±0.1) × 10 −11 , (1.1± 0.1) × 10 −9 , (1.9 ± 0.1) × 10 −9 , and (1.5±0.1) × 10 −9 cm 3 molecule −1 s −1 , for collisions with He, Ne, Ar, N 2 and CO, respect dispersed fluorescence spectra recorded, it is found that collision-induced vibrational deactivation occurs in collisions with Ar, N 2 , and CO, and that this process is more efficient with these quenchers than with He.

Collisional deactivation of CO+ A 2Π (ν = 0–2) by He, Ne, Ar, N2, and CO

Abstract Collisional deactivation rate constants of CO + A 2 Π (ν = 0 and 2) by He, Ne, Ar, N 2 , and CO have been determined by using a time-resolved laser-induced fluorescence technique. The results were combined with the previously determined ν = 1 rate constants to obtain an interesting ν dependence of the rate constant. It has been found that the collisional deactivation rates by Ar, N 2 , and CO are as large as the Langevin gas kinetic ones and almost independent of the vibrational level of CO + A 2 Π. Contrary to the case of Ar, N 2 , and CO, the rate constants by He and Ne have been found to be two or three orders of magnitude smaller than the Langevin and sensitive to the vibrational level. The results are related to the availability of a charge transfer state, which is energetically allowed with the former group of quenchers, while it is not with the latter group of molecules.

Mechanisms and rate constants of the collisional deactivation of CO+(A 2Π,v) by He and Ar

Collisional deactivation processes of CO+(A  2Π,v) by He and Ar are investigated in detail using both a time‐resolved laser induced fluorescence and a threshold electron‐secondary ion coincidence technique. Three deactivation mechanisms, pure vibrational relaxation, internal conversion, and charge transfer reaction, are identified. The time‐resolved fluorescence from both the initially photoexcited and vibrationally relaxed levels of CO+ A 2Π makes clear the two distinct vibrational relaxation mechanisms: indirect two‐step population of the lower levels in the CO+ (A)+He system and direct transition to the lower levels in the CO+(A)–Ar system. Threshold electron‐secondary ion coincidence (TESICO) experiments demonstrate that the charge transfer reactions CO+ (A,v)+Ar→Ar++CO contribute significantly to the overall fluorescence quenching by Ar.

Interferogram amplitude modulation technique for selective detection of transient species with a continouus-scan Fourier-transform spectrometer

Abstract A new interferogram amplitude modulation (IAM) technique for a Fourier-transform spectrometer with a continuous-scan interferometer was devised. This technique is useful for selective detection of transient species produced in ac discharge plasmas. Infrared emission spectra due to the Δν = 1 bands of the vibrationally excited CO molecule, the fundamental band of the OH radical, and the 5g-4f band of Rydberg H2 were recorded to demstrate selectivity of this method.

Search for New Methods for Assignment of Complex Molecular Spectra and a Program Package for Simulation of Molecular Spectra

Recent development of spectroscopic instruments has allowed us to obtain a large amount of spectral data in machine readable forms. High resolution molecular spectra contain abundant information on structures and dynamics of molecules. However, extraction of such useful information necessitates a procedure of spectral assignment in which each spectral line is assigned a set of quantum numbers. This procedure has traditionally been performed by making use of regular patterns that are obviously seen in the observed spectrum. However, we often encounter complex spectra in which such regular patterns may not be readily discerned. The purpose of the present work is to search for new methods which can assist in assigning such complex molecular spectra. We wish to devise computer aided techniques for picking out regular patterns buried in a list of observed values which look like randomly distributed. We hope that we may make use of various fruits of information sciences and may depend on great computational power of modern computers

Collision-induced transitions between two spin-orbit states of CO+ A 2Π(v=1) with He

Abstract Collision-induced spin-orbit relaxation in a vibronically excited state CO + A 2 Π 1 2 ( v =1) + He→CO + A 2 Π 3 2 ( v =1) + He has been investigated by using a flowing afterglow/time-resolved LIF technique. The rate constants k 12 ( 2 Π 1 2 → 2 Π 3 2 ) and k 21 ( 2 Π 3 2 → 2 Π 1 2 ) are determined to be k 12 + k 21 = (3.0 ± 0.3) × 10 −10 cm 3 molecule −1 s −1 . A comparison of the results with those for the neutral system NO X 2 Π( v = 0)_+ He suggests that neither the positive charge on the ion nor the vibrational energy plays significant roles in the fast spin-orbit relaxation process.