Hiroyuki Horiguchi

Interatomic potentials of HgXe van der Waals complex formed in supersonic jets as studied by laser induced fluorescence spectroscopy

The laser induced fluorescence spectra of HgXe formed in a supersonic free jet of a He/Xe/Hg mixture were observed to determine the interatomic potentials between Hg and Xe in the X 10+, A 30+, and B 31 states. The dissociation energies for the X, A, and B states are 254, 1457, and 172 cm−1, respectively, with the equilibrium interatomic distances of 4.25, 3.25, and 4.47 A for the respective states. It is found that the potential shape for the X and B states can be represented in good approximation by a Morse function, though this function may not reproduce the potential for the A state especially in the vicinity of high vibrational levels (v′>16).

Infrared diode laser kinetic spectroscopy of the CCO radical in the X̃ 3Σ− state generated by the excimer laser photolysis of carbon suboxide

The ν1 band of the CCO radical in the X 3Σ− ground electronic state has been observed in the gas phase by diode laser kinetic spectroscopy. The CCO radical was generated by the 193 or 248 nm excimer laser photolysis of carbon suboxide. By fixing ground state parameters to the microwave values, the band origin and the vibrational changes of the rotational (αB=B0−B1) and spin–spin interaction (αλ=λ1−λ0) constants have been determined to be 1970.864 34(95), 0.003 075 4(85), and 0.008 3(12) in cm−1 with 2.5 standard errors in parentheses.

Vibrational distribution of CO and NO excited by electronic‐to‐vibrational energy transfer collisions with Hg(6 3P1 and 6 3P0)

The initial vibrational distributions of CO and NO excited by electronic‐to‐vibrational (E–V) energy transfer collisions with Hg1* (Hg in the 6 3P1 state) and Hg0* (Hg in the 6 3P0 state) have been determined by the measurements of the IR emission spectra of CO and NO utilizing a modulation technique. The Hg resonant radiation to excite Hg to Hg1* in Ar(N2) –CO or –NO mixtures was modulated in its intensity with a frequency in the range of 120 Hz to several kHz. Observation of the resulting in‐phase and quadrature components of the IR emission made it possible to separate the contribution of the initial vibrational excitation to each level from that of the vibrational relaxation. In Hg*1–CO collisions, Hg1*→Hg*0 transition occurs with simultaneous excitation of CO to the v=1 level. The fraction of the electronic energy of Hg* converted to the vibrational energy of CO or NO are 27%, 32%, and 31% for Hg*0–CO, Hg*1– and Hg*0–NO collisions, respectively. The vibrational distributions resemble the Poisson type...

Vibrational Relaxation of NO(X2\varPi) in the States of v=2∼10

The NO overtone emission spectra induced by collisions with Hg(63P1) have been observed in order to determine the vibrational deactivation rate of NO(X2\varPi, v=2~10) from phase-shift measurement. Although the vibration-to-translation energy transfer rate of excited NO is several orders of magnitude larger than that of excited CO, the vibration-to-vibration energy transfer rates of both molecules are of a similar magnitude. No experimental evidence was found for the existence of a very efficient near-resonant vibration-to-vibration energy transfer of NO(2\varPiΩ, v=n)+NO(2\varPi3/2, v=0)→NO(2\varPiΩ, v=n-1)+NO(2\varPi1/2, v=1), in which \varOmega=1/2 or 3/2 and the vibrational energy mismatch is reduced by the electronic transition from the 2\varPi3/2 to 2\varPi1/2 state.

Vibrational excitation of N2 by the spin-orbit relaxation of Hg(63P1→ 63P0)

The lifetime of Hg(63P0) in a gas mixture of Ar + N2 at room temperature was measured by a phase-shift method. A mixture containing a trace of Hg vapour was illuminated by 253.7 nm radiation, whose intensity was modulated at a frequency in the range of 120–1000 Hz, and the resulting a.c. component of Hg(63P0) concentration was monitored by a lock-in system. The lifetime is inversely proportional to the square root of the 253.7 nm radiation intensity. This is attributable to accumulation of N2 in the v= 1 level through the spin-orbit relaxation Hg(63P1)+ N2(v= 0)→ Hg(63P0)+ N2(v= 1), and the reverse of this reaction results in shortening of the lifetime. The accumulation of N2 in the v= 1 level is due to the fact that N2(v= 1) is deactivated by a factor of about 102 less efficiently than Hg(63P0). The observed dependence of the lifetime on the 253.7 nm intensity made it possible to deduce the rate constant of the relaxation. The result agreed with the value determined from the lifetime measurement of Hg(63P1) in N2. Thus, it is concluded that the spin-orbit relaxation of Hg(63P1) in N2 consists of the electronic-to-vibrational energy transfer. The reciprocal lifetime of N2(v= 1) was determined to be 1.2 ± 0.3 s–1 in the mixture of 1 Torr N2+ 9 Torr Ar. This leads to the estimate that the collision probability for deactivation of N2(v= 1) on the wall of a quartz cell is 1 × 10–4.

Luminescence spectrum and kinetics of laser-excited HgNH3 complex

Abstract When an Hg/NH 3 gas mixture was irradiated by laser light around 260 nm, luminescence appeared in the range of 290–360 nm. The spectrum of the luminescence was almost the same as that induced by the Hg photosensitized reaction of NH 3 , and thus, the laser-induced luminescence was assigned to emission of an excited HgNH 3 complex. The luminescence spectrum as well as the excitation spectrum could be reproduced by the Franck-Condon factors calculated from the bound-free transition between the Hg-NH 3 repulsive ground state and the excited bound state. Time-evolution measurements on the luminescence induced by the pulsed irradiation of the laser indicated that initially formed HgNH 3 excimer had to make a collisional transition to a state which could emit the luminescence around 340 nm.

Laser-induced luminescence from an excited HgNH3 complex

Abstract When a Hg/NH 3 mixture is irradiated at 260 nm or longer wavelengths luminescence appears around 340 nm. The luminescence originates from an excited HgNH 3 complex formed through a bound—free transition. Both the luminescence excitation spectrum and the dispersed spectrum have been analysed in terms of postulated potentials for the ground and excited-state HgNH 3 complexes.

A Laser Technique for State-Selected Time-of-Flight Analysis by Pseudo-Random Modulation

A laser technique has been developed for the time-of-flight (TOF) analysis of state-selected atomic or molecular beams. The technique was applied to TOF measurements of Na atoms seeded in supersonic rare gas beams. When a dye Baser excited Na atoms in one of the hyperfine levels of the 32S1/2 state, this level was completely depopulated as a result of the optical pumping effect. This depopulation could be detected at a downstream position by the same Baser light, since the optically-pumped atoms were transparent, and thus the TOF spectrum could be derived by taking the time correlation between the pseudo-randomly modulated pump laser light and the depopulation detected by LIF. A preliminary scattering experiment of Na by CO2 and SF6 was carried out to confirm the effectiveness of this method.

On the isotope effect of the electronic‐to‐vibrational energy transfer from Hg(6 3P) to CO and NO

The electronic−to−vibrational energy transfer from Hg(6 3P) to 13CO and 15NO is reported for collisions of excited mercury atoms with CO and NO. (AIP)