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Journal Articles

Solvent extraction of technetium(VII) and rhenium(VII) using a hexaoctylnitrilotriacetamide extractant

Shimojo, Kojiro; Suzuki, Hideya; Yokoyama, Keiichi; Yaita, Tsuyoshi; Ikeda, Atsushi

Analytical Sciences, 36(12), p.1435 - 1437, 2020/12

 Times Cited Count:0 Percentile:100(Chemistry, Analytical)

Liquid-liquid extraction for the removal of pertechnetate ($$^{99}$$TcO$$_{4}$$$$^{-}$$) and perrhenate (ReO$$_{4}$$$$^{-}$$) is reported using tripodal extractant $$N,N,N',N',N'',N''$$-hexa-$$n$$-octylnitrilotriacetamide (HONTA) composed of three amide groups and a tertiary amine. The extraction behavior was compared with those using alkyldiamideamines (ADAAM(Oct) and ADAAM(EH)), and the commercial amine-type extractant, trioctylamine (TOA). HONTA quantitatively extracted $$^{99}$$TcO$$_{4}$$$$^{-}$$ and ReO$$_{4}$$$$^{-}$$ in the pH range from 1.0 to 2.5 by co-extraction of protons. Extraction performance of extractants was improved in the order of HONTA $$>$$ ADAAM(Oct) $$>$$ ADAAM(EH) $$>$$ TOA. $$^{99}$$TcO$$_{4}$$$$^{-}$$ and ReO$$_{4}$$$$^{-}$$ in the extracting phase were successfully stripped using neutral aqueous solutions as the receiving phase, and the extraction ability of HONTA was maintained after five repeated uses.

Journal Articles

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri. A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:2 Percentile:17.5(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Quantum optimal control of rovibrational excitations of a diatomic alkali halide; One-photon vs. two-photon processes

Kurosaki, Yuzuru*; Yokoyama, Keiichi

Universe (Internet), 5(5), p.109_1 - 109_15, 2019/05

 Times Cited Count:0 Percentile:100(Astronomy & Astrophysics)

Regarding rovibrational transitions of diatomic alkali haride molecules, optimal waveform of laser electric field was calculated on the basis of the optimal control theory. In this study, we implemented the polarizability term into the Hamiltonian, which defines the field-molecule interaction. As a result, we obtained waveforms causing both one- and two-photon processes in a relatively high electric field regime, while waveforms causing only one-photon process was observed in a weak filed regime as well as the previous study. These results imply that the effect of two-photon process is successfully taken into account in the optimal control theory calculation. Now we can expect more reliable calculation even for strong laser field.

Journal Articles

A Quasiclassical trajectory calculation to compute the reaction cross section and thermal rate constant for the cesium exchange reaction $$^{133}$$CsI + $$^{135}$$Cs $$rightarrow$$ $$^{133}$$Cs + I$$^{135}$$Cs

Kobayashi, Takanori*; Matsuoka, Leo*; Yokoyama, Keiichi

Computational and Theoretical Chemistry, 1150, p.40 - 48, 2019/02

 Times Cited Count:0 Percentile:100(Chemistry, Physical)

One of important research targets in the development of cesium isotope separation system is design of recovery process of cesium atom. Relevant to this research target, the reaction cross section and reaction rate constant of a cesium exchange reaction through collision of the cesium iodide molecules with cesium atoms are calculated by a quasi-classical trajectory calculation based on a potential energy surface obtained by quantum chemistry calculations. Consequently, the rate constant is calculated to be 3.6 $$times$$ 10$$^{-10}$$ cm$$^{3}$$molecule$$^{-1}$$s$$^{-1}$$, as large as collision rate in the present condition. In addition, slightly positive temperature dependence is observed in the rate constant. This behavior is explained with the long-range attractive force and effect of subsequent dissociation process.

Journal Articles

Absorbent property of fullerene for cesium isotope separation investigated using X-ray photoelectron spectroscopy

Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi

Progress in Nuclear Science and Technology (Internet), 5, p.161 - 164, 2018/11

For nuclear transmutation of cesium-135 ($$^{135}$$Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom onto the surface of fullerene (C$$_{60}$$) film has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (XPS). The results were compared with those of CsI. It was found that Cs penetrates into C$$_{60}$$ deep bulk. In contrast, CsI deposits on shallow surface. Furthermore, XPS spectra were measured as a function of Ar$$^{+}$$-sputtering time in order to know Cs concentration profiles in deep region. Results showed that Cs penetrates into deep region of several hundreds ${AA}$.

Journal Articles

A Quasi-classical trajectory calculation for the cesium exchange reaction of $$^{133}$$CsI (v = 0, j = 0) + $$^{135}$$Cs $$rightarrow$$ $$^{133}$$Cs + I$$^{135}$$Cs

Kobayashi, Takanori*; Matsuoka, Leo*; Yokoyama, Keiichi

Nippon Enerugi Gakkai-Shi, 96(10), p.441 - 444, 2017/10

To investigate the reaction cross section of the cesium exchange reaction of $$^{133}$$CsI (v = 0, j = 0) + $$^{135}$$Cs $$rightarrow$$ $$^{133}$$Cs + I$$^{135}$$Cs, we performed quasi-classical trajectory calculations on the potential energy surface calculated by the ab initio molecular orbital theory. The potential energy surface shows that intermediate Cs$$_{2}$$I is formed without entrance barrier and has two equivalent Cs-I bonds. The reaction cross sections decrease monotonically with increasing collision energy. The rate constant k (v = 0, j = 0) was estimated to be about 3$$times$$10$$^{-10}$$cm$$^{3}$$ molecule$$^{-1}$$s$$^{-1}$$ at temperatures ranging from 500 to 1200K and a slight negative temperature dependence was observed.

Journal Articles

Current situations and discussions in Japan in relation to the new occupational equivalent dose limit for the lens of the eye

Yokoyama, Sumi*; Hamada, Nobuyuki*; Hayashida, Toshiyuki*; Tsujimura, Norio; Tatsuzaki, Hideo*; Kurosawa, Tadahiro*; Nabatame, Kuniaki*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; et al.

Journal of Radiological Protection, 37(3), p.659 - 683, 2017/09

 Times Cited Count:10 Percentile:14.28(Environmental Sciences)

Since the International Commission on Radiological Protection recommended reducing the occupational equivalent dose limit for the lens of the eye in 2011, there have been extensive discussions in various countries. This paper reviews the current situations in radiation protection of the ocular lens and the discussions on the potential impact of the new lens dose limit in Japan. Topics include historical changes to the lens dose limit, the current situations in occupational lens exposures (e.g., in medical workers, nuclear workers, and Fukushima nuclear power plant workers) and measurements, and the current status of biological studies and epidemiological studies on radiation cataracts. Our focus is on the situations in Japan, but we believe such information sharing will be useful in many other countries.

Journal Articles

Quantum optimal control of the isotope-selective rovibrational excitation of diatomic molecules

Kurosaki, Yuzuru*; Yokoyama, Keiichi

Chemical Physics, 493, p.183 - 193, 2017/08


 Times Cited Count:3 Percentile:77.34(Chemistry, Physical)

Electric field of laser pulses which gives maximum selectivity in the isotope-selective rovibrational excitation of lithium chloride molecules is calculated. Applying the optimal control theory, we calculate optimal electric field to produce mixture of LiCl-35 ($$nu$$=0, $$J$$=0) and LiCl-37 ($$nu$$=1, $$J$$=1) from molecular ensemble of LiCl-35 ($$nu$$=0, $$J$$=0) and LiCl-37 ($$nu$$=0, $$J$$=0). As a result, it is found that electric field which permit rotational excitations only gives high yield in the selective excitation compared to the electric field which permit both rotational and vibrational excitations.

Journal Articles

Theoretical study of the adsorption of Cs, Cs$$^+$$, I, I$$^-$$, and CsI on C$$_{60}$$ fullerene

Kobayashi, Takanori; Yokoyama, Keiichi

Journal of Nuclear Science and Technology, 53(10), p.1489 - 1493, 2016/10

 Times Cited Count:5 Percentile:39.29(Nuclear Science & Technology)

Theoretical investigation for the adsorption of the cesium atom (Cs), the cesium iodide molecule (CsI), the iodine atom (I), the cesium cation (Cs$$^+$$), and the iodide anion (I$$^-$$) onto the surface of a single fullerene molecule (C$$_{60}$$) are reported. A hybrid exchange-correlation functional using the Coulomb-attenuating method (CAM-B3LYP) is employed. The adsorption energies, i.e., the opposite of enthalpy change through adsorption, are calculated to be 34, 3, 2, 11, and 12 kcal mol$$^{-1}$$ for Cs, CsI, I, Cs$$^+$$, and I$$^-$$, respectively. The equilibrium constant for Cs is calculated to be 7$$times$$10$$^3$$ atm$$^{-1}$$ at the temperature of 1000 K and is seven orders of magnitude higher than that for CsI, indicating that the C$$_{60}$$ molecule adsorb the Cs atom highly selectively against the CsI molecule.

JAEA Reports

Theoretical study of the Cs isotope exchange reaction of CsI + Cs'$$rightarrow$$ Cs + ICs' (Contract research)

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

JAEA-Research 2015-014, 7 Pages, 2015/12


To discuss the exchange reaction of Cs isotope by CsI + Cs'$$rightarrow$$ Cs + ICs', the structure and chemical properties of Cs$$_2$$I intermediate and potential energy surface are calculated using M06/def2-TZVPPD density functional calculation. The calculation shows that the reaction to the intermediate has no barrier and the two Cs-I bonds of Cs$$_2$$I are chemically equivalent. Thus, the collision of CsI + Cs' results in Cs exchange with the high probability.

Journal Articles

Addendum report of the JHPS expert committee on radiation protection of the lens of the eye, 2; When and how should the dosimetry of beta $$H_{rm p}$$(3) be made?

Akahane, Keiichi*; Iimoto, Takeshi*; Ichiji, Takeshi*; Iwai, Satoshi*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; Kurosawa, Tadahiro*; Tatsuzaki, Hideo*; Tsujimura, Norio; et al.

Hoken Butsuri, 50(4), p.257 - 261, 2015/12

In a mixed field of photon and beta radiations, the same dose assigned to skin is normally assigned to the dose to the lens of the eye as a conservative estimate of H$$_{p}$$(3). In exceptional cases that a very high beta dose might be imparted of the same order with the dose limit, however, the conservatively biased dose must be too limiting, and thereby an accurate estimate of beta $$H_{rm p}$$(3) is desirable. This article presents a practical proposal of when and how the dosimetry of beta $$H_{rm p}$$(3) should be made.

Journal Articles

Superdeformation in $$^{35}$$S

Go, Shintaro*; Ideguchi, Eiji*; Yokoyama, Rin*; Kobayashi, Motoki*; Kisamori, Keiichi*; Takaki, Motonobu*; Miya, Hioyuki*; Ota, Shinsuke*; Michimasa, Shinichiro*; Shimoura, Susumu*; et al.

JPS Conference Proceedings (Internet), 6, p.030005_1 - 030005_4, 2015/06

Journal Articles

Isotope-selective dissociation of diatomic molecules by terahertz optical pulses

Ichihara, Akira; Matsuoka, Leo*; Segawa, Etsuo*; Yokoyama, Keiichi

Physical Review A, 91(4), p.043404_1 - 043404_7, 2015/04

 Times Cited Count:10 Percentile:38.8(Optics)

We propose a new method for isotope-selective dissociation of diatomic molecules in the gas phase by using two kinds of terahertz-pulse fields. The first field consists of a train of pulses, which composes a frequency comb, excites the selected isotope into highly-rotationally excited state. The second intense pulse field dissociates the excited molecule by further rotational excitations. We performed wave-packet computations using the lithium chlorides $$^{7}$$Li$$^{35}$$CL and $$^{7}$$Li$$^{37}$$Cl to demonstrate the applicability of our method. Nearly 20% of $$^{7}$$Li$$^{37}$$Cl in the lowest rovibrational state is dissociated in the designed pulse fields, while the dissociation probability is negligible in $$^{7}$$Li$$^{35}$$Cl. This method is expected to be applicable to other diatomic molecules, and to molecular ensembles whose rotational states spread in energy.

Journal Articles

Quantum control of isotope-selective rovibrational excitation of diatomic molecules in the thermal distribution

Ichihara, Akira; Matsuoka, Leo*; Kurosaki, Yuzuru; Yokoyama, Keiichi

Optical Review, 22(1), p.153 - 156, 2015/02

 Times Cited Count:6 Percentile:56.04(Optics)

We propose a method to excite the rovibrational states of diatomic molecules in the gas-phase isotope-selectively by optical pulses. In this method, the rotational state of the selected isotope molecule is excited by the terahertz frequency comb, and the vibrational state of high J molecule is excited via the fundamental transitions in the P-branch by using the second pulse. The applicability of the proposed method is demonstrated by computer simulations using the LiCl molecules in the thermal distribution at 70 K.

Journal Articles

Dynamic discrimination of oriented molecules controlled with the nonresonant dynamic Stark effect induced by a single-cycle THz pulse

Kurosaki, Yuzuru; Akagi, Hiroshi; Yokoyama, Keiichi

Physical Review A, 90(4), p.043407_1 - 043407_9, 2014/10

 Times Cited Count:3 Percentile:83.18(Optics)

Journal Articles

Interim report of the JHPS expert committee on radiation protection of the lens of the eye, 2; The Dosimetry method for the lens of the eye of workers in Japan

Akahane, Keiichi*; Iimoto, Takeshi*; Ichiji, Takeshi*; Iwai, Satoshi*; Oguchi, Hiroyuki*; Ono, Kazuko*; Kawaura, Chiyo*; Tatsuzaki, Hideo*; Tsujimura, Norio; Hamada, Nobuyuki*; et al.

Hoken Butsuri, 49(3), p.153 - 156, 2014/09

A brief review is given of the history and methodology of external dosimetry for the lens of the eye. Under the 1989 revision to domestic radiological protection regulations, the concept on the effective dose equivalent and the dose limit to the lens of the eye (150 mSv/y) both introduced in ICRP 1977 recommendations has changed nationwide the external monitoring methodology in non-uniform exposure situations to the trunk of a radiological worker. In such situations, often created by the presence of a protective apron, the worker is required to use at least two personal dosemeters, one worn on the trunk under the apron and the other, typically, at the collar over the apron. The latter dosemeter serves the dual purpose of providing the dose profile across the trunk for improved effective dose equivalent assessment and of estimating the dose to lens of the eye. The greater or appropriate value between $$H_{rm p}$$(10) and $$H_{rm p}$$(0.07), given by the dosemeter, is generally used as a surrogate of $$H_{rm p}$$(3).

Journal Articles

Optical frequency comb opens up highly efficient isotope separation of long-lived fission products; The Quantum walk to reduce radioactive waste

Yokoyama, Keiichi; Matsuoka, Leo*

Nippon Genshiryoku Gakkai-Shi, 56(8), p.525 - 528, 2014/08

With respect to the isotope separation of cesium, one of the long-lived fission products, the background, principle, feasibility, and research activity in Kansai Photon Science Institute are described.

Journal Articles

Theoretical study on isotope-selective dissociation of the lithium chloride molecule using a designed terahertz-wave field

Ichihara, Akira; Matsuoka, Leo; Kurosaki, Yuzuru; Yokoyama, Keiichi

JPS Conference Proceedings (Internet), 1, p.013093_1 - 013093_4, 2014/03

Isotope-selective dissociation of the lithium chloride (LiCl) molecule was investigated by quantum mechanical calculations. $$^7$$Li$$^{35}$$Cl in the initial rovibrational state (v=0,J=0) was excited by an optical frequency comb whose spectral frequencies were tuned to the rotational transition frequencies of $$^7$$Li$$^{35}$$Cl. $$^7$$Li$$^{37}$$Cl was not highly excited by the comb because of the difference of the transition frequencies. The time evolution of rovibrational population was evaluated using the close-coupling method during the comb irradiation. The dissociation process in the second pulse was calculated by the wave packet method. The amplitudes of close-coupling were employed as the input of the wave packet computation. The dissociation probability was estimated by absorbing wave packet using a damping function. By the optical pulses adopted, about 60% of $$^7$$Li$$^{35}$$Cl was dissociated. The dissociation probability of $$^7$$Li$$^{37}$$Cl was less than 2%t.

Journal Articles

An Analytic formula for describing the transient rotational dynamics of diatomic molecules in an optical frequency comb

Ichihara, Akira; Matsuoka, Leo*; Kurosaki, Yuzuru; Yokoyama, Keiichi

Chinese Journal of Physics, 51(6), p.1230 - 1240, 2013/12

We derived an analytic expression for evaluating the transient rotational dynamics of diatomic molecules in an optical frequency comb which is tuned to induce a series of pure rotational transitions. The formulation is based on the quantum delta-kicked rotor model, and the orthogonality of delta functions at different time is assumed. The formulation is performed with the matrix decomposition technique. We derived the probability amplitude composed of term corresponding to a Bessel function of the first kind and other oscillating terms. The time dependence of obtained transition probability is shown as a staircase function.

Journal Articles

Physical implementation of quantum cellular automaton in a diatomic molecule

Matsuoka, Leo; Yokoyama, Keiichi

Journal of Computational and Theoretical Nanoscience, 10(7), p.1617 - 1620, 2013/07

 Times Cited Count:4 Percentile:75.05(Chemistry, Multidisciplinary)

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