Yukio Adachi

Two-photon absorption study of 1,3,5-hexatriene by cars and CSRS

Abstract Two-photon absorption spectra of trans- and cis-1,3,5-hexatrienes in the liquid state have been observed in the frequency range of 2ω = 30000–50000 cm−1, by analyzing the interference effect of Raman and two-photon resonances in the CARS and CSRS lineshape. In both isomers, a broad two-photon absorption with a maximum absorptivity of about 10−50 cm4 s photon−1 molecule−1 was determined to be a few thousand cm−1 higher than an intense dipole-allowed transitions (11Bu ← 11Ag or 11B2 ← 11A1) near 40000 cm−1. This band is most probably assigned to the two-photon-allowed state corresponding to the lowest excited singlet already established to be 21Ag or 21A1 in larger homologues. The relative ordering of the 11B and 21A levels is discussed.

Resonance CARS and CSRS line shapes of Ni(II)‐octaethylporphyrin

CARS and CSRS of Ni(II)‐octaethylporphyrin in benzene solution have been measured in the resonance condition with the first visible absorption (Q) band. The line shape behavior of some nontotally symmetric vibrations has been investigated by changing the pump frequency ω1 in the absorbing region, with the particular elaboration on 1308 cm−1 (A2g) line, which shows the inverse polarization and is most strikingly enhanced in ordinary resonance Raman. The observed line shapes were remarkably different between the CARS and CSRS by the common pumping frequency ω1. The whole result has been consistently interpreted in terms of the vibronic theory of Raman intensity, on the basis of semiclassical perturbation theory by Lotem et al. The effect of concurrent resonances of ω1 and ω3 (or ω2) has been demonstrated in a definite manner.

Resonance CARS Study of Electronic Excited Molecules

Abstract There has been much progress in the vibrational spectroscopic study of short-lived chemical species and electronic excited states in the last decade [1, 2]. Most of those studies employed Raman scattering method by recourse to the resonance enhancement associated with the transient electronic absorption. TR3 is now widely known aB standing for “Time-Resolved Resonance Raman” spectroscopy.

Optogalvanic spectrum of CO. II. The rotational structure of the L 1Π state

The Q branch and P, R branches of the 4pπL 1Π–3sσB 1Σ+ transition of CO have been newly observed by high resolution and low resolution optogalvanic spectroscopy, respectively. The value of the Λ‐type doubling constant in the L 1Π state has been determined as q=0.0213±0.0012 cm−1. An accidental perturbation was discovered in the Π− component of the L 1Π state. The Angstrom (0–3) and (0–4) bands were also observed.

Optogalvanic measurement of the cathode-fall region of Kr hollow cathode discharge

Optogalvanic observation of the Stark shift of the Kr 8d[3/2]20-5p[3/2]2 atomic line has been carried out on a Kr hollow cathode discharge in a discharge tube with a cylindrical cathode, at a fill pressure of 1 to 6 Torr (1 Torr = 133.322 Pa), and a discharge current from 1 to 10 mA, to reveal the linear decrease of electric field with radial distance from the cathode surface. Values of current density, charge density, and other discharge parameters have been derived and their behavior has been compared with theoretical formula; it is concluded that a major role is played by the photons from the negative-glow region. Unusual features observed in the discharge at 1 Torr pressure and above 5 mA of current have been attributed to the effect of Penning ionization of sputtered copper atoms.

Sn ←S1 and S1→S0 resonance CARS spectra of perylene in the S1 state

Resonance CARS spectrum of perylene in the first excited singlet (S1 ) state was observed in solution at room temperature. The observed shifts of Raman frequencies from the ground (S0 ) state values were related to the results of the PPP‐SCF‐CI MO calculation and the normal coordinate calculation. The experiment, intended to observe the resonance CARS signal of the S0 state, was found to give the signal predominated by the lines of the S1 state. It was also concluded that the peculiar feature originating from the simultaneous role of the pump beam depleted the molecules in the S0 state, populated the S1 state, and caused the resonance effect on CARS through the intense S1 →S0 transition.

Space Charge Distribution in the Cathode Fall Region of an Ar Hollow Cathode Discharge

The electric field above the cathode surface of an Ar hollow cathode discharge has been measured by optogalvanic Stark spectroscopy. The field depends on the radial position of illumination and describes the radial distribution of the space charge density, ρ(r), as ρ(r) = –Ar + B, where r is the radial position and the parameters A and B are positive. The values of A and B increase with the discharge current, but the width of the cathode fall region remains nearly constant at about 1.02 ± 0.03 mm for a brass cathode of 5 mm i. d.

Optogalvanic observation of the CO W 1Π–B 1∑+ transition

The rotational structure of the W 1Π–B 1∑+ (0–0) band was resolved and the values of spectroscopic parameters were derived as B’0 =1.5549±0.0068 cm−1, r0=0.1257±0.0003 nm, and ν00=15 891.6±0.6 cm−1. The observation of the W 1Π–B 1∑+ (0–0) band supports Ogawa and Ogawa’s assignment that the W 1Π state is the first member of the nsσ Rydberg series converging to the A2 Πi state of CO+ ion. The W 1Π–B 1∑+ (1–0) band, on the other hand, was not observed with expected intensity and the presence of dissociative perturbation has been suggested.

Observation of inter-rydberg K 1Σ+−B 1Σ+ and L 1Π-B 1Σ+ transitions of co by optogalvanic spectroscopy

Abstract The inter-Rydberg 4pσ K 1 Σ + −3sσ B 1 Σ + and 4pπ L 1 Π-3sσB 1 Σ + transitions of CO have been newly observed at 16134 and 16357 cm −1 , respectively, by optogalvanic spectroscopy of the hollow cathode discharge of He/CO mixture gas.

Doppler‐free optogalvanic spectrum of He2 b 3Πg–f 3Δu transition

Doppler‐Free Lamb dip and intermodulated spectra of He2 b 3Πg–f 3Δu transition have been observed by the technique of optogalvanic spectroscopy. The analysis of the triplet splittings of rotational lines yielded the values of spin‐orbit (A), spin–spin (λζ and λ⊥⊥) and spin‐orbit (γ) coupling constants of AΠ=−6.753±0.26, λζ=3.069±0.37, λ⊥⊥=−4.480±0.03, γ=−0.009±0.02 GHz for the b 3Πg state, and AΔ=−0.073±0.10, λζ=0276±0.27, and γ=0.016±0.03 GHz for the f 3Δu state. The Λ‐type doubling in the b 3Πg state was found negligible. The derived values for the b 3Πg state are compared with those for the H2 c 3Πu state which has the optical electron in the same 2pπ orbital as He2 b 3Πg state, and the departure of the electron configuration in the He2 b 4Πg state from the united atom orbital (UAO) is discussed.