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Journal Articles

Quantum paramagnet near spin-state transition

Tomiyasu, Keisuke*; Ito, Naoko*; Okazaki, Ryuji*; Takahashi, Yuki*; Onodera, Mitsugi*; Iwasa, Kazuaki*; Nojima, Tsutomu*; Aoyama, Takuya*; Ogushi, Kenya*; Ishikawa, Yoshihisa*; et al.

Advanced Quantum Technologies (Internet), 1(3), p.1800057_1 - 1800057_7, 2018/12

Spin-state transition, also known as spin crossover, plays a key role in diverse systems. In theory, the boundary range between the low- and high-spin states is expected to enrich the transition and give rise to unusual physical states. However, no compound that realizes a nearly degenerate critical range as the ground state without requiring special external conditions has yet been experimentally identified. This study reports that the Sc substitution in LaCoO3 destabilizes its nonmagnetic low-spin state and generates an anomalous paramagnetic state accompanied by the enhancement of transport gap and magneto-lattice-expansion as well as the contraction of Co-O distance with the increase of electron site transfer. These phenomena are not well described by the mixture of conventional low- and high-spin states, but by their quantum superposition occurring on the verge of a spin-state transition.

Journal Articles

Correlation between photoeletron and photoion in ultrafast multichannel photoionization of Ar

Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*

AIP Conference Proceedings 1702, p.090021_1 - 090021_4, 2015/12

 Times Cited Count:0 Percentile:0

We theoretically investigate coherent dynamics of ions created through ultrafast multichannel photoionization from a viewpoint of photoelectron-photoion correlation. The model calculation on single-photon ionization of Ar reveals that the coherent hole dynamics in Ar$$^+$$ associated with a superposition of the spin-orbit states $$^2P_J$$ (J = 3/2 and 1/2) can be identified by monitoring only the photoion created by a Fourier-transform limited extreme ultraviolet (EUV) pulse with the 9-fs pulse duration, while the coherence is lost by a chirped EUV pulse. It is demonstrated that by coincidence detection of the photoelectron and photoion the coherent hole dynamics can be extracted even in the case of ionization by a chirped EUV pulse with the sufficiently wide bandwidth.

Journal Articles

Photoelectron-photoion correlation in ultrafast multichannel photoionization of Ar

Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*

Journal of Physics B; Atomic, Molecular and Optical Physics, 47(19), p.195602_1 - 195602_9, 2014/10

 Times Cited Count:2 Percentile:15.6(Optics)

Ultrafast multichannel single-photon ionization of Ar is investigated theoretically by a model calculation incorporating correlation between the photoelectron and photoion. It is shown that the coherent hole dynamics in Ar$$^+$$ associated with a superposition of the spin-orbit states can be observed by using a Fourier-transform limited laser pulse for ionization, while the coherence is degraded or lost by chirping a laser pulse. We demonstrate that the coherent hole dynamics can be retrieved even in the case of a chirped laser pulse, by labeling the photoion dynamics with the counterpart photoelectron energy.

Journal Articles

Assessment of doses from external exposure in contaminated areas resulting from the Fukushima Daiichi Nuclear Power Plant accident

Takahara, Shogo; Kimura, Masanori; Kinase, Sakae; Ishikawa, Jun; Suyama, Kenya; Hosoyamada, Ryuji; Homma, Toshimitsu

Progress in Nuclear Science and Technology (Internet), 3, p.25 - 29, 2012/10

Dose assessment is one of the important issues to make decisions in contaminated areas resulting from the Fukushima Daiichi Nuclear Power Plant accident. The doses to inhabitants of contaminated areas should be assessed prospectively and retrospectively taking into account the impact from various exposure pathways. The external exposure from deposited radioactive materials of short-lived and long-lived is one of the most important pathways. In the present study, the radionuclide compositions have been evaluated by source term analysis taking into account 54 radionuclides. This analysis consists in evaluating the inventory and the fraction of the radionuclides that were released into the atmosphere. On the assumption that dose rate may be decreased due to the radioactive decay as well as weathering effects, we have assessed the dose for future and past at the contaminated areas. The assessed values are almost consistent with the measured ones during the first month.

Journal Articles

Effects of ion-beam irradiation on germination and growth of seedlings of red pepper "Hirosaki zairai"

Tomikawa, Masaru*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei

JAEA-Review 2010-065, JAEA Takasaki Annual Report 2009, P. 73, 2011/01

Oral presentation

Effects of ion-beam irradiation on germination and growth of seedlings of redpepper "Hirosakizairai"

Tomikawa, Masaru*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Nozawa, Shigeki; Narumi, Issei

no journal, , 

no abstracts in English

Oral presentation

Effect of ion beam irradiation to seeds on generation and growth in the seedling of capsicum native variety in Hirosaki

Maeda, Tomoo*; Tomikawa, Masaru*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei

no journal, , 

no abstracts in English

Oral presentation

Expression of mutations in the M2 generation of red pepper "Hirosaki zairai" irradiated with ion beam

Sato, Yusuke*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Yoshihara, Ryohei; Nozawa, Shigeki; Narumi, Issei

no journal, , 

no abstracts in English

Oral presentation

Expression of mutations in progeny of ion-beam irradiated Capsicum native variety in Hirosaki

Sato, Yusuke*; Maeda, Tomoo*; Honda, Kazushige*; Saga, Koichi*; Ishikawa, Ryuji*; Akita, Yusuke; Nozawa, Shigeki; Hase, Yoshihiro; Narumi, Issei

no journal, , 

no abstracts in English

Oral presentation

Wavepacket of correlated photoelectron and ion core in ultrafast multichannel photoionization

Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*

no journal, , 

Photoelectron spectra in ultrafast photoionization exhibits a broadened spectra feature leading to the spectral overlap. In this situation, multiple ionic states are superposed. However, we need to take account of the coupling between the photoelectron continuum and the ionic states. In this study, we derive the wavepacket representation of the correlated photoelectron and ion core states and show the numerical results on the ionization of a rage gas atom into the spin-orbit split states.

Oral presentation

Ultrafast multichannel photoionization described by wavepacket of correlated photoelectron and ion core

Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*

no journal, , 

In ultrafast photoionization, the spectra width in the photoelectron spectrum is broadended and then the peaks are overlapped, resulting in the coherent superposition of correlated photoelectron and ionic states. In this study, the wave packet picture of correlated photoelectron and ion core is formulated. Numerical simulation is carried out for photoionization of Ar into two spin-orbit split states as a model case. The temporal evolution of ion core dynamics following photoelectron emission will be discussed.

Oral presentation

Photoelectron-photoion correlation in ultrafast multichannel photoionization of Ar

Itakura, Ryuji; Fushitani, Mizuho*; Hishikawa, Akiyoshi*; Sako, Tokuei*

no journal, , 

We theoretically investigate how such an effect appears in ultrafast ionization, by explicitly treating the correlation between a photoelectron and a photoion. One-photon ionization of Ar by a linearly polarized EUV pulse is considered as a model case. The mechanism governing the coherence in the ion will be revealed by examining the temporal variation in the hole density of Ar$$^+$$ in a photoelectron-energy resolved manner.

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