Faculty Profiles - HISHIKAWA, Akiyoshi

Papers - HISHIKAWA, Akiyoshi

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Radiative lifetime measurements of the B2∑+ state of BaH by laser spectroscopy Reviewed

L. E. Berg, K. Ekvall, A. Hishikawa, S. Kelly

Physica Scripta Vol. 55 ( 3 ) page： 269 - 272 1997

Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Swedish Academy of Sciences

By applying laser resonance methods in the near infrared wavelength region around 900 nm, a time-resolved experiment has been performed on the low lying B 2∑+ state of barium hydride. The radiative lifetime is shown to vary with the rotational quantum number due to perturbations between the low lying A′ 2Δ, A 2∏ and B 2∑+ states. The following lifetime was obtained for the BaH molecule, where local perturbations are assumed to be negligible: τ(B 2∑+(ν′ = 0, J = 5.5)) = 125 ± 2 ns.

DOI： 10.1088/0031-8949/55/3/003

Scopus

Laser spectroscopy of SrH. Time-resolved measurements of the A(2)Pi state Reviewed

LE Berg, K Ekvall, A Hishikawa, S Kelly, C McGuinness

CHEMICAL PHYSICS LETTERS Vol. 255 ( 4-6 ) page： 419 - 424 1996.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

In the near-infrared and red wavelength region around 680-760 nm, the spectrum of the A(2) Pi-X(2) Sigma transition of gaseous SrH appears. By applying laser spectroscopic methods, a time-resolved experiment has been performed on the low-lying A(2) Pi state of strontium hydride. No local influences on the A(2) Pi state were found due to interactions with the low-lying A'(2) Delta state, as in the case of the BaH molecule. The following zero-pressure lifetime was obtained for the SrH molecule: tau(A(2) Pi(1/2) (upsilon'=0))=33.8+/-1.9 ns.

DOI： 10.1016/0009-2614(96)00376-4

Web of Science

VUV photofragment excitation spectroscopy: Dynamics on dissociative potential surface of OCS Reviewed

K Ohde, A Hishikawa, K Yamanouchi

JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA Vol. 79 page： 433 - 436 1996.5

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The measurements of the photofragment excitation (PHOFEX) spectrum of jet-cooled OCS were extended toward the 152.6 and 150.6 nm peaks in the (1) Sigma(+)-(1) Sigma(+) transition. The PHOFEX spectra were recorded by scanning the wavelength of a tunable vacuum ultraviolet (VU) photolysis laser while probing the S(S-1) product by a second laser. Due to the efficient cooling of the sample in the free-jet expansion and the high-resolving power of the VUV laser, the homogeneous broadening of the dissociative state was derived directly from the observed PHOFEX spectrum. Based on the measured peak width, the lifetimes (tau) of the dissociative states at 152.6 and 150.6 nm were determined to be tau approximate to 50 and 31 fs. The PHOFEX peaks were found to exhibit an asymmetric line profile, and a fitting to a Fano line formula led to the asymmetry parameters, q= -8.1(2) and -13.0(6), for the 152.6 and 150.6 nm peaks, indicating a considerable mixing of the continuum and discrete states in that particular energy region. On the basis of the determined lifetimes and q values, together with the corresponding values for the 154.5 nm peak, tau approximate to 140 fs and q = -3.5(9), the dissociation dynamics on the repulsive (1) Sigma(+) surface was inferred.

DOI： 10.1016/0368-2048(96)02888-5

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PHOTODISSOCIATION AND VIBRATIONAL DYNAMICS OF OCS IN THE VUV REGION Reviewed

K YAMANOUCHI, K OHDE, A HISHIKAWA, CD PIBEL

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 68 ( 9 ) page： 2459 - 2464 1995.9

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

The photofragment excitation (PHOFEX) spectrum of jet-cooled OCS was remeasured for the 154.5 nm peak in the (1) Sigma(+)-(1) Sigma(+) transition by scanning a tunable vacuum ultraviolet (VUV) laser wavelength in the deep VUV region and by probing the S(S-1) product with a second laser. Due to the efficient cooling of the sample in the free-jet expansion and the high-resolving power of the VUV laser, the homogeneous broadening of the dissociative state was derived directly from the observed PHOFEX spectrum. Based on the measured peak width, the lifetime (tau) of the dissociative state was determined to be tau congruent to 0.14 ps. The profile of the PHOFEX peak was found to be asymmetric and was fit to a Fano line profile to derive the value of the asymmetry parameter, q=-3.5(9), which indicates a considerable mixing of the continuum and discrete states in that particular energy region. A Fourier-transform analysis was also performed for the whole distinct absorption feature in the 160-140 nm region measured by McCarthy and Vaida [J. Phys. Chem., 92, 5875 (1988)], and the period of the vibrational motion on the dissociative potential-energy surface was derived to be 41 fs. Using these pieces of experimental evidence, the dissociation dynamics on the repulsive (1) Sigma(+) surface in the 154.5 nm region was inferred.

DOI： 10.1246/bcsj.68.2459

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MONTE-CARLO STUDY OF POPULATION AND ALIGNMENT RELAXATION BY TRAPPED LINE RADIATION Reviewed

A HISHIKAWA, T FUJIMOTO, P ERMAN

PHYSICAL REVIEW A Vol. 52 ( 1 ) page： 189 - 196 1995.7

ENERGY-DEPENDENT COLLISION CROSS-SECTION AS ESTIMATED FROM TEMPERATURE-DEPENDENT RATE COEFFICIENT - DISALIGNMENT OF EXCITED NEON ATOMS BY NEON COLLISIONS Reviewed

Y ISHITANI, H ISHIDA, T KITAGAWA, A HISHIKAWA, T FUJIMOTO

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Vol. 26 ( 19 ) page： L671 - L675 1993.10

Language：English Publisher：IOP PUBLISHING LTD

Laser-induced-fluorescence spectroscopy has been applied to a neon discharge plasma. A disalignment rate coefficient for 2p2 (Paschen notation; 2p5 3p configuration) atoms for neon atom collisions was determined at several atom temperatures (77-640 K). From the temperature dependence of the rate coefficient we estimate the cross section which explicitly depends on collision energy. It is found that the cross section has a positive energy dependence, which suggests that the OMEGA = 0 and 1 molecular potential curves correlating to the 2P2 State of neon are repulsive by about 100 cm-1 where these curves split by 10-20 cm-1.

DOI： 10.1088/0953-4075/26/19/007

Web of Science

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI-SAPPHIRE LASER - RADIATIVE LIFETIMES OF THE A(2)PI,B(2)SIGMA(+), AND C(2)PI STATES OF BACL Reviewed

LE BERG, A HISHIKAWA, A KARAWAJCZYK, T OLSSON

JOURNAL OF MOLECULAR SPECTROSCOPY Vol. 160 ( 2 ) page： 593 - 595 1993.8

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI SAPPHIRE LASER RADIATIVE LIFETIMES OF THE A(2)PI, B(2)SIGMA(+) AND C(2)PI STATES OF BAF Reviewed

LE BERG, T OLSSON, JC CHANTELOUP, A HISHIKAWA, P ROYEN

MOLECULAR PHYSICS Vol. 79 ( 4 ) page： 721 - 725 1993.7

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS LTD

A time resolved experiment on the lowest lying states of barium fluoride has been performed by applying laser resonance methods in the near infrared and green-blue wavelength regions. The A2PI and B2SIGMA+ states have been examined using Ti:sapphire laser excitations in the 710-850 nm wavelength region. The C2PI state was examined using the 496.5 nm Ar+ laser line and the lifetime of this state was in accordance with earlier measurements. The lifetimes obtained for the BaF molecule were: A2PI3/2, 46.1 +/- 0.9 ns; B2SIGMA+, 41.7 +/- 0.3 ns.

DOI： 10.1080/00268979300101571

Web of Science

LIFETIME MEASUREMENTS OF EXCITED MOLECULAR-STATES USING A TI-SAPPHIRE LASER - RADIATIVE LIFETIMES OF THE B(2)SIGMA+ STATE AND C(2)PI STATE OF BABR Reviewed

LE BERG, K EKVALL, E HEDIN, A HISHIKAWA, A KARAWAJCZYK, S KELLY, T OLSSON

CHEMICAL PHYSICS LETTERS Vol. 209 ( 1-2 ) page： 47 - 51 1993.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

The barium bromide monohalide has been studied by using laser resonance methods in the near-infrared and green-blue wavelength regions. The low-lying B 2SIGMA+ state has been investigated in a time-resolved experiment using a Ti:sapphire laser operating around 900 nm. No influence on the radiative lifetime due to the B 2SIGMA interaction with the A'2DELTA-A 2PI complex was observed. The radiative lifetime of the C2PI state was examined using the 514.5 nm Ar+ laser line. The derived lifetime of this state was in agreement with earlier measurements. The following lifetimes were obtained for the BaBr molecule: B 2SIGMA+ 123.2 +/- 0.5 ns and C2PI(3/2)16.9+/-0.1 ns.

DOI： 10.1016/0009-2614(93)87199-d

Web of Science

PREDISSOCIATION EFFECTS IN THE A2-DELTA AND B2-SIGMA- STATES OF CD Reviewed

M DANIELSSON, P ERMAN, A HISHIKAWA, M LARSSON, E RACHLEWKALLNE, G SUNDSTROM

JOURNAL OF CHEMICAL PHYSICS Vol. 98 ( 12 ) page： 9405 - 9411 1993.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Lifetimes have been measured for a large number of rotational levels of the A2DELTA and B2SIGMA-states in CD using the high frequency deflection technique. Four B-state levels are found to be influenced by predissociation by rotation which demands a lower value of the CD dissociation energy. The B state predissociations have also been studied using ab initio calculations. The A state levels above the dissociation limit are found to be weakly predissociated through interaction with the ground state continuum. The results are compared with earlier lifetime investigations of CH.

DOI： 10.1063/1.464372

Web of Science

THE ELECTRONIC-TRANSITION MOMENT AND THE OSCILLATOR STRENGTH OF THE SIH+ A1-PI-X1-SIGMA+ TRANSITION Reviewed

A HISHIKAWA, A KARAWAJCZYK

JOURNAL OF MOLECULAR SPECTROSCOPY Vol. 158 ( 2 ) page： 479 - 481 1993.4

EXPERIMENTAL-OBSERVATION OF DISALIGNMENT EFFECTS IN RADIATION TRAPPING PROCESSES Reviewed

P ERMAN, A HISHIKAWA

PHYSICA SCRIPTA Vol. 46 ( 4 ) page： 348 - 353 1992.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SWEDISH ACAD SCIENCES

Alignment effects at electron excitation measurements of atomic lifetimes have been studied at 20 keV energy using the High Frequency Deflection technique and a plastic polarizer. Disalignment associated with radiation trapping is observed directly for the first time. It has been pointed out that our previous results of the lifetime of the Ar 2p(i) levels might possibly have been influenced not only by radiation trapping itself but also by this "radiative disalignment". However, this influence has been found to be negligible thanks to small intrinsic alignment in almost all lines of noble gases investigated.

DOI： 10.1088/0031-8949/46/4/006

Web of Science

INFLUENCE OF RADIATION TRAPPING ON THE POLARIZATION DEGREE OF THE HE-I 501.6 NM LINE IN COLLISION SPECTROSCOPY Reviewed

A HISHIKAWA, H MIZUNO, M TANI, R OKASAKA

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Vol. 25 ( 16 ) page： 3419 - 3431 1992.8

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The influence of radiation trapping on the polarization degree of the emission of the He I 501.6 nm line (3(1)P-2(1)S) is studied by experiments and a simulation. In the experiments, a particle (proton or electron) beam was injected into a helium gas cell. The accelerating energy was 100 keV for protons and 1.5, 2.5 and 5.0 keV for electrons. The polarization degree measured as a function of gas pressure showed a minimum at a certain gas pressure in accordance with results obtained by Hasselkamp et al. A Monte Carlo simulation method to treat the non-resonance line of the resonance state in a finite gas cell is presented. This simulation reproduces the minimum of the polarization degree as seen from experiments. We conclude that this minimum is caused by the asymmetry in the spatial distribution of atoms excited by collisions. We attempt to estimate a polarization degree not influenced by radiation trapping by fitting the simulated results to the experimental ones.

DOI： 10.1088/0953-4075/25/16/004

Web of Science

The g-u interference oscillations observed in the emission cross sections and the optical polarizations in he+—he collisions Reviewed

M. Tani, A. Hishikawa, R. Okasaka

Journal of Physics D: Applied Physics Vol. 24 ( 6 ) page： 1359 - 1376 1991.3

Language：English Publishing type：Research paper (scientific journal)

We have observed emission radiation from helium atoms excited in He+-He collisions by the direct and electron capture processes over the energy range 0.5-20 keV.The relative emission cross sections for transitions 21,3P-31,3S, 21,3S-31,3P and 21,3P-31,3Dhave been determined. Degrees of optical polarization have also been determined for theP- and D-state excitations. The emission cross section of the direct excitation and that ofthe electron capture excitation show oscillations against impact energy, which are inantiphase with each other. The polarization degrees for both processes are of nearly thesame magnitude and show weak oscillations in antiphase with each other. The oscillationsof the cross section and those of the polarization degree are in phase in some cases andin antiphase in other cases. These oscillations are interpreted as due to the interferencebetween the gerade and ungerade states of the helium quasimolecular ion. From theamplitude ratio and the phase correlation between the oscillations of the cross section andthose of the polarization degree we find that the predominant g-u interference pai r is nΠg-Πu. © IOP Publishing Ltd.

DOI： 10.1088/0953-4075/24/6/022

Scopus

THE G-U INTERFERENCE OSCILLATIONS OBSERVED IN THE EMISSION CROSS-SECTIONS AND THE OPTICAL POLARIZATIONS IN HE+-HE COLLISIONS Reviewed

M TANI, A HISHIKAWA, R OKASAKA

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Vol. 24 ( 6 ) page： 1359 - 1376 1991.3

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

We have observed emission radiation from helium atoms excited in He+-He collisions by the direct and electron capture processes over the energy range 0.5-20 keV. The relative emission cross sections for transitions 2(1,3)P-3(1,3)S, 2(1,3)S-3(1,3)P and 2(1,3)P-3(1,3)D have been determined. Degrees of optical polarization have also been determined for the P- and D-state excitations. The emission cross section of the direct excitation and that of the electron capture excitation show oscillations against impact energy, which are in antiphase with each other. The polarization degrees for both processes are of nearly the same magnitude and show weak oscillations in antiphase with each other. The oscillations of the cross section and those of the polarization degree are in phase in some cases and in antiphase in other cases. These oscillations are interpreted as due to the interference between the gerade and ungerade states of the helium quasimolecular ion. From the amplitude ratio and the phase correlation between the oscillations of the cross section and those of the polarization degree we find that the predominant g-u interference pairs is PI-g-PI-u.

DOI： 10.1088/0953-4075/24/6/022

Web of Science

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