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Journal Articles

Three-dimensional electronic structures and the metal-insulator transition in Ruddlesden-Popper iridates

Yamasaki, Atsushi*; Fujiwara, Hidenori*; Tachibana, Shoichi*; Iwasaki, Daisuke*; Higashino, Yuji*; Yoshimi, Chiaki*; Nakagawa, Koya*; Nakatani, Yasuhiro*; Yamagami, Kohei*; Aratani, Hidekazu*; et al.

Physical Review B, 94(11), p.115103_1 - 115103_10, 2016/11

AA2016-0587.pdf:2.55MB

 Times Cited Count:11 Percentile:24.6(Materials Science, Multidisciplinary)

In this study, we systematically investigate three-dimensional(3D) momentum-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr$$_{n+1}$$Ir$$_{n}$$O$$_{3n+1}$$ using soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO$$_{2}$$-plane structure. This transition occurs when the spin-orbit-coupled $$j_{eff}$$ = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO$$_{3}$$ and $$k_{z}$$-dependent oscillations of photoelectron intensity in Sr$$_{3}$$Ir$$_{2}$$O$$_{7}$$. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole Brillouin zone and provides a panoramic view of electronic structures.

Journal Articles

Journal Articles

Measurement of the $$^{77}$$Se($$gamma$$, n) cross section and uncertainty evaluation of the $$^{79}$$Se(n, $$gamma$$) cross section

Kitatani, Fumito; Harada, Hideo; Goko, Shinji*; Iwamoto, Nobuyuki; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*; Igashira, Masayuki*

Journal of Nuclear Science and Technology, 53(4), p.475 - 485, 2016/04

 Times Cited Count:2 Percentile:57.25(Nuclear Science & Technology)

Journal Articles

Cross section measurement for photo nuclear reaction using laser Compton-scattering $$gamma$$-ray

Kitatani, Fumito; Harada, Hideo; Goko, Shinji*; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*

JAEA-Conf 2014-002, p.57 - 62, 2015/02

Journal Articles

Partial photoneutron cross sections for $$^{207,208}$$Pb

Kondo, Takeo*; Utsunomiya, Hiroaki*; Goriely, S.*; Iwamoto, Chihiro*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Lui, Y.-W.*; et al.

Nuclear Data Sheets, 119, p.310 - 313, 2014/05

 Times Cited Count:1 Percentile:85.28(Physics, Nuclear)

Journal Articles

Photoneutron cross sections for Mo isotopes; A Step toward a unified understanding of($$gamma$$,n) and (n,$$gamma$$)reactions

Utsunomiya, Hiroaki*; Goriely, S.*; Kondo, Takeo*; Iwamoto, Chihiro*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Lui, Y.-W.*; et al.

Physical Review C, 88(1), p.015805_1 - 015805_6, 2013/07

 Times Cited Count:38 Percentile:5.5(Physics, Nuclear)

Journal Articles

$$gamma$$-ray strength function method; A Way from photoneutron emission to radiative neutron capture

Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Yamagata, Tamio*; Iwamoto, Chihiro*; Goriely, S.*; Daoutidis, I.*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Iwamoto, Nobuyuki; et al.

Proceedings of 14th International Symposium on Capture $$gamma$$-Ray Spectroscopy and Related Topics, p.505 - 514, 2013/05

Journal Articles

Total and partial photoneutron cross sections for Pb isotopes

Kondo, Takeo*; Utsunomiya, Hiroaki*; Goriely, S.*; Daoutidis, I.*; Iwamoto, Chihiro*; Akimune, Hidetoshi*; Okamoto, Akiyuki*; Yamagata, Tamio*; Kamata, Masaki*; Ito, Osamu*; et al.

Physical Review C, 86(1), p.014316_1 - 014316_7, 2012/07

 Times Cited Count:26 Percentile:13.83(Physics, Nuclear)

Using quasi-monochromatic laser-Compton scattering $$gamma$$ rays, total photoneutron cross sections were measured for $$^{206,207,208}$$Pb near neutron threshold with a high-efficiency 4$$pi$$ neutron detector. Partial $$E$$1 and $$M$$1 photoneutron cross sections along with total cross sections were determined for $$^{207,208}$$Pb at four energies near threshold by measuring anisotropies in photoneutron emission with linearly-polarized $$gamma$$ rays. The $$E$$1 strength dominates over the $$M$$1 strength in the neutron channel where $$E$$1 photoneutron cross sections show extra strength of the pygmy dipole resonance in $$^{207,208}$$Pb near the neutron threshold corresponding to 0.32-0.42% of the Thomas-Reiche-Kuhn sum rule. Several $$mu$$$$_N^{2}$$ units of B($$M$$1)$$uparrow$$ strength were observed in $$^{207,208}$$Pb just above neutron threshold, which correspond to an $$M$$1 cross section less than 10% of the total photoneutron cross section.

Journal Articles

Determination of the number of pulsed laser-Compton scattering photons

Kondo, Takeo*; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Yamagata, Tamio*; Okamoto, Akiyuki*; Harada, Hideo; Kitatani, Fumito; Shima, Tatsushi*; Horikawa, Ken*; Miyamoto, Shuji*

Nuclear Instruments and Methods in Physics Research A, 659(1), p.462 - 466, 2011/12

 Times Cited Count:18 Percentile:12.26(Instruments & Instrumentation)

We measured pulse-height spectra of 16.7 MeV laser-Compton scattering photons with a 6"$$times$$5" NaI(Tl) detector for blank and three lead materials of 75.8, 50.9, and 25.9% transmissions at the NewSUBARU facility to investigate how the original Poisson distribution of the pulsed photons is modified after passing through thick-target materials. We present a well-prescribed method of determining the number of incident photons within 3.5% accuracy based on the response of the NaI(Tl) detector to the pulsed photon beams.

Journal Articles

Photoneutron cross sections for $$^{118-124}$$Sn and the $$gamma$$-ray strength function method

Utsunomiya, Hiroaki*; Goriely, S.*; Kamata, Masaki*; Akimune, Hidetoshi*; Kondo, Takeo*; Ito, Osamu*; Iwamoto, Chihiro*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Lui, Y.-W.*; et al.

Physical Review C, 84(5), p.055805_1 - 055805_6, 2011/11

 Times Cited Count:31 Percentile:10.37(Physics, Nuclear)

Photoneutron cross sections were measured for $$^{118}$$Sn, $$^{119}$$Sn, $$^{120}$$Sn, $$^{122}$$Sn, and $$^{124}$$Sn near neutron threshold with quasi-monochromatic laser-Compton scattering $$gamma$$-rays. A systematic analysis of the present photoneutron data and existing neutron-capture data is made using the $$gamma$$-ray strength function on the basis of the HFB+QRPA model of E1 strength supplemented with a pygmy dipole resonance, which was deduced from a previous study on $$^{116}$$Sn and $$^{117}$$Sn. Radiative neutron capture cross sections for two radioactive nuclei, $$^{121}$$Sn and $$^{123}$$Sn, are deduced through the $$gamma$$-ray strength function method.

Journal Articles

The $$gamma$$SF method

Utsunomiya, Hiroaki*; Goriely, S.*; Akimune, Hidetoshi*; Yamagata, Tamio*; Kondo, Takeo*; Iwamoto, Chihiro*; Okamoto, Akiyuki*; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; et al.

AIP Conference Proceedings 1377, p.255 - 259, 2011/10

 Percentile:100

Journal Articles

Photoneutron cross sections for Au

Ito, Osamu*; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Yamagata, Tamio*; Kondo, Takeo*; Kamata, Masaki*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; et al.

AIP Conference Proceedings 1377, p.362 - 364, 2011/10

 Percentile:100

Journal Articles

Application of the $$gamma$$SF method to palladium

Utsunomiya, Hiroaki*; Goriely, S.*; Arteaga, D. P.*; Daoutidis, I.*; Akimune, Hidetoshi*; Yamagata, Tamio*; Kondo, Takeo*; Iwamoto, Chihiro*; Kamata, Masaki*; Ito, Osamu*; et al.

AIP Conference Proceedings 1377, p.450 - 452, 2011/10

 Percentile:100

Journal Articles

Photoneutron cross sections for Au revisited; Measurements with laser Compton scattering $$gamma$$-rays and data reduction by a least-squares method

Ito, Osamu*; Utsunomiya, Hiroaki*; Akimune, Hidetoshi*; Kondo, Takeo*; Kamata, Masaki*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; et al.

Journal of Nuclear Science and Technology, 48(5), p.834 - 840, 2011/05

Photoneutron cross section measurements were made for Au in the entire energy range of the ($$gamma$$,n) channel based on a direct neutron-counting technique with quasi-monochromatic $$gamma$$-rays produced in inverse Compton-scattering of laser photons with relativistic electrons. The data were analyzed with a least-squares method to deduce photoneutron cross sections. The analysis significantly reduced experimental uncertainties compared with those resulted from the photon difference method. The result is compared with the previous data by direct neutron-counting with $$gamma$$-rays produced in positron annihilation in flight and by photoactivation with bremsstrahlung. The present data are in good agreement with the previous data near neutron threshold, while there remain some discrepancies between the present and the previous data above 10 MeV.

Journal Articles

$$gamma$$-ray strength function method and its application to $$^{107}$$Pd

Utsunomiya, Hiroaki*; Goriely, S.*; Akimune, Hidetoshi*; Harada, Hideo; Kitatani, Fumito; Goko, Shinji*; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*; Kondo, Takeo*; Ito, Osamu*; et al.

Physical Review C, 82(6), p.064610_1 - 064610_5, 2010/12

 Times Cited Count:30 Percentile:11.17(Physics, Nuclear)

The $$gamma$$-ray strength function method ($$gamma$$SF method) is devised to indirectly determine radiative neutron capture cross sections for radioactive nuclei. This method is applied here to the $$^{107}$$Pd case. Photoneutron cross sections were measured for $$^{105,106,108}$$Pd near neutron threshold with quasi-monochromatic laser-Compton-scattering $$gamma$$-ray beams. These photoneutron cross sections as well as the reverse radiative neutron capture cross sections for $$^{104,105}$$Pd are used to provide constraints on the $$^{107}$$Pd(n,$$gamma$$) $$^{108}$$Pd cross section.

Journal Articles

Striking behavior of photoneutron cross sections for $$^{90}$$Zr near threshold

Utsunomiya, Hiroaki*; Goriely, S.*; Akimune, Hidetoshi*; Yamagata, Tamio*; Kondo, Takeo*; Iwamoto, Chihiro*; Ito, Osamu*; Kamata, Masaki*; Io, Masanori*; Kususe, Koichi*; et al.

AIP Conference Proceedings 1377, p.447 - 449, 2010/10

 Percentile:100

Journal Articles

Photoneutron cross sections for $$^{96}$$Zr; A Systematic experimental study of photoneutron and radiative neutron capture cross sections for zirconium isotopes

Utsunomiya, Hiroaki*; Goriely, S.*; Akimune, Hidetoshi*; Harada, Hideo; Kitatani, Fumito; Goko, Shinji; Toyokawa, Hiroyuki*; Yamada, Kawakatsu*; Kondo, Takeo*; Ito, Osamu*; et al.

Physical Review C, 81(3), p.035801_1 - 035801_5, 2010/03

 Times Cited Count:32 Percentile:10.02(Physics, Nuclear)

This manuscript presents photoneutron cross sections for $$^{96}$$Zr. Combining the present data with the previously published Zr data, we investigated the $$gamma$$-ray strength function for zirconium isotopes systematically. We present a unified picture of the $$gamma$$-ray strength function that consists of the HFB + QRPA model of E1 strength accompanied by an extra M1 strength attributable to giant M1 resonance. It is shown that the $$gamma$$-ray strength function reproduces both (g,n) and (n,g) cross sections for Zr isotopes consistently.

Journal Articles

Photodisintegration of $$^{80}$$Se; Implications for the s-process branching at $$^{79}$$Se

Makinaga, Ayano*; Utsunomiya, Hiroaki*; Goriely, S.*; Kaihori, Takeshi*; Goko, Shinji*; Akimune, Hidetoshi*; Yamagata, Tamio*; Toyokawa, Hiroyuki*; Matsumoto, Tetsuro*; Harano, Hideki*; et al.

Physical Review C, 79(2), p.025801_1 - 025801_8, 2009/02

 Times Cited Count:20 Percentile:20.02(Physics, Nuclear)

Photoneutron cross sections were measured for $$^{80}$$Se immediately above the neutron separation energy with quasimonochromatic $$gamma$$-ray beams to experimentally constrain the E1 $$gamma$$ strength function for $$^{79}$$Se. Two sets of the $$gamma$$ strength function and the level density that equally meet the experimental constraint predict largely different neutron capture cross sections for $$^{79}$$Se. Based on the Maxwell-averaged cross sections of the latest compilation complemented with the predicted cross sections for $$^{79}$$Se, we calculated $$sigma$$N values of the main s-process component using a phenomenological model and deduced empirical abundances of the weak s-process component.

Journal Articles

Measurements of photon mass attenuation coefficients for Ge and BGO crystals at 10 MeV

Harada, Hideo; Kitatani, Fumito; Goko, Shinji; Hara, Kaoru*; Toyokawa, Hiroyuki*; Kaihori, Takeshi*; Utsunomiya, Hiroaki*

Journal of Nuclear Science and Technology, 45(11), p.1228 - 1232, 2008/11

 Times Cited Count:3 Percentile:70.64(Nuclear Science & Technology)

A system measuring the photo-absorption cross sections using the HHS and LCS $$gamma$$-rays has been developed. The data for Ge and BGO crystals were measured for 10.0 MeV $$gamma$$-rays, and the effectiveness of the system for the measurements of the photo-absorption cross sections was demonstrated. The system will be very powerful tool to measure the photon-absorption cross sections especially for high energy photons, whose energy is variable between 1.6 and 40 MeV. The result also shows that there are not so significant discrepancies between the evaluated photo-absorption cross sections and the measurements at 10 MeV as was pointed in case of U-238 at least for Ge and BGO crystals.

Journal Articles

Photoneutron cross sections for $$^{80}$$Se; Implications for the s-process thermometer

Makinaga, Ayano*; Utsunomiya, Hiroaki*; Kaihori, Takeshi*; Yamagata, Tamio*; Akimune, Hidetoshi*; Goriely, S.*; Toyokawa, Hiroyuki*; Matsumoto, Tetsuro*; Harano, Hideki*; Harada, Hideo; et al.

Nuclear Physics A, 805(1-4), p.564 - 566, 2008/06

Photoneutron cross sections were measured for $$^{80}$$Se near the neutron threshold energy with quasi-monochromatic $$gamma$$ rays. Using the $$^{80}$$Se($$gamma$$,$$n$$) cross section as experimental constraints on the E1 $$gamma$$ strength function, we estimate the neutron capture rates for $$^{79}$$Se. The solar abundance ratio of s-only nuclides $$^{80}$$Kr and $$^{82}$$Kr are analyzed in terms of the s-process branching at $$^{79}$$Se within the local approximation. The corresponding temperature and neutron density regimes are discussed in the light of the s-process scenario in massive stars.

29 (Records 1-20 displayed on this page)