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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:1 Percentile:2.09(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

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

Nihon 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

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:6 Percentile:49.65(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

JAEA-Research-2015-014.pdf:2.46MB

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.

Oral presentation

Theoretical investigation of the Cs exchange reaction between CsI molecule and Cs atom

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

no journal, , 

To investigate the possibility of the Cs exchange reaction between CsI molecule and Cs atom, we have analyzed the Cs-I-Cs triatomic molecule by using quantum chemistry calculation. And, by using the newly developed capture model, the Cs exchange reaction rate and its temperature dependence were also estimated. The stabilization energy for CsICs formation is calculated as 12 kcal mol$$^{-1}$$, which is much smaller than the calculated Cs-I bond energy of 82 kcal mol-1(spin-orbit correlation is not included). However, the bond lengths of both Cs-I are optimized as the same value (3.57 A). That is, Cs of CsI and colliding Cs atom cannot be distinguished if the triatomic structure is formed. And 2-dimensional potential energy surface around CsI against Cs atom shows that the reaction has no entrance barrier. The reaction rate was estimated to be the same value as the collision rate and little temperature dependence would be expected.

Oral presentation

Theoretical study of the Cs exchange reaction rate constant of Cs + CsI $$rightarrow$$ CsI + Cs

Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

no journal, , 

To investigate the possibility of the Cs exchange reaction, we have analyzed the Cs-I-Cs triatomic molecule by using quantum chemistry calculation. Furthermore, by using the newly developed capture model, the Cs exchange reaction rate and its temperature dependence were estimated. 2-dimensional potential energy surface around CsI against Cs atom shows that the reaction has no entrance barrier. The reaction rate was found to be close to the collision rate and to have a little temperature dependence would be expected.

Oral presentation

Theoretical study of absorption of Cs and CsI to fullerenes

Kobayashi, Takanori; Yokoyama, Keiichi

no journal, , 

We have a plan for isotope separation of $$^{135}$$Cs by using the difference of rotational constants of CsI. In the plan, the adsorbent which can adsorb Cs species-selectively is desirable for the recovery of $$^{135}$$Cs after isotope-selective dissociation process of CsI. Paying attention to the difference of the chemical nature of CsI and Cs, fullerenes would be expected to be desirable as the adsorptive material. To confirm the idea, we have calculated the adsorption energy of Cs, CsI etc. to C$$_{60}$$ fullerene by using quantum chemistry calculation. We have also calculated the adsorption energy to the cluster model of illite, a kind of minerals which exists in soil and is known as a Cs$$^{+}$$ adsorbent. The results show that C$$_{60}$$ fullerene would be suitable to adsorb Cs atom in many CsI molecules. On the contrary, illite or other minerals would not be suitable for our purpose.

Oral presentation

Theoretical study of C$$_{60}$$ fullerene as the adsorbent of Cs

Kobayashi, Takanori; Yokoyama, Keiichi

no journal, , 

We have a plan for isotope separation of $$^{135}$$Cs using the difference of rotational constants of CsI. In the plan, the adsorbent which can adsorb Cs species-selectively is desirable for the recovery of $$^{135}$$Cs after isotope-selective dissociation process of CsI. Paying attention to the difference of the chemical nature of CsI and Cs, fullerenes would be expected to be desirable as the adsorptive material. To confirm the idea, we have calculated the adsorption energy of Cs, CsI etc. to C$$_{60}$$ fullerene using quantum chemistry calculation. We have also calculated the adsorption energy of a cluster model of illite, a kind of minerals which exists in soil and is known as a Cs$$^+$$ adsorbent. The results show that C$$_{60}$$ fullerene would be suitable to adsorb Cs atom in many CsI molecules. In the paper, we will discuss the thermochemical stability of the adducts.

Oral presentation

Nonlinear optical response of molecules rotationally excited by impulsive Raman scattering

Yokoyama, Keiichi; Kobayashi, Takanori*

no journal, , 

We report a consideration on the non-linear optical response of molecules rotationally excited by impulsive Raman scattering. An ensemble of molecules which are cascadedly excited and de-excited among the rotational levels by a several numbers of Raman transitions is not uniform in spatial coherence and depend on the number of transition the molecule undergoes. Therefore, there is a possibility to obtain signal waveforms which cannot be explained by the conventional analysis method which ignores the non-locality of the density operator. In this study, we adopted non-local density operator to calculate non-linear optical response in such case. As a result, we predicted that significant angular dependence of observed signal appear due to the spherical wave of input pump laser pulse. We qualitatively confirmed the analysis reproduce the observed waveform.

Oral presentation

Time and spatial resolved measurement of metal particle melting under laser irradiation using synchrotron radiation X-ray imaging method

Shobu, Takahisa; Shiro, Ayumi*; Yasuda, Ryo*; Koizumi, Yasuyuki; Mizutani, Haruki; Kobayashi, Takanori; Muramatsu, Toshiharu

no journal, , 

no abstracts in English

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