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Oral presentation

Metal nano-particle formation by femtosecond laser filamentation

Nakashima, Nobuaki*; Yamanaka, Kenichi*; Yatsuhashi, Tomoyuki*; Taniguchi, Seiji*; Saeki, Morihisa; Oba, Hironori

no journal, , 

no abstracts in English

Oral presentation

Laser chemistry for Eu recovery

Nakashima, Nobuaki*; Yokoyama, Keiichi; Yatsuhashi, Tomoyuki*; Sakota, Kenji*; Iwakura, Izumi*

no journal, , 

Studies on photo-reduction of trivalent europium, Eu(III), is revisited by nanosecond lasers at various wavelengths with a Ti:Sapphire, excimer, and dye lasers. We measured the quantum yields, wavelength dependence, and power dependence. As a result, we found that the photo-reduction is induced by a two-photon absorption with a relatively high efficiency as to be observed directly with eyes. Also, the quantum yield of one-photon reduction at 308 nm was determined to be 0.6. These results indicate that highly efficient and selective separation techniques are possible for f-electron elements using multi-photon absorption process induced by laser light.

Oral presentation

Reduction of Eu$$^{3+}$$ by multiphoton excitation in alcohol solutions

Matsuda, Shohei; Nakashima, Nobuaki*; Yokoyama, Keiichi; Yatsuhashi, Tomoyuki*; Chosrowjan, H.*; Taniguchi, Seiji*; Somekawa, Toshihiro*

no journal, , 

The photoredox reactions of lanthanides as a photochemical separative technique proposed in the 1970s are expected to be applied for recovery and recycling of rare metals and nuclear fuel reprocessing. In this study, Eu$$^{3+}$$ ions in methanol and ethanol solutions were reduced to Eu$$^{2+}$$ ions upon irradiation with nanosecond laser pulses. Eu$$^{2+}$$ was observed when the laser wavelength was tuned to f-f transition bands at 394 and 465 nm. The formation rate of Eu$$^{2+}$$ was proportional to the square of the incident laser intensity, indicating that the photoreduction is induced by a two-photon process. The efficiency of the photoreduction in ethanol was higher than that in methanol.

Oral presentation

Fluence dependence of multiphoton reduction of Eu(III) via f-f transition

Matsuda, Shohei; Nakashima, Nobuaki*; Yokoyama, Keiichi; Yatsuhashi, Tomoyuki*; Chosrowjan, H.*; Taniguchi, Seiji*; Somekawa, Toshihiro*

no journal, , 

The photochemical reactions of lanthanide and actinide ions are expected to be utilized for recovery and recycling of rare earths, and nuclear fuel reprocessing. Heading towards research for implementation of photochemical purification, a unified evaluation of the efficiency of multiphoton processes is required. In this study, we have evaluated the fluence dependence of photoreduction of Eu(III) more precisely than before by measuring the beam profile of the excitation laser. The reduction rate of Eu(III)$$rightarrow$$Eu(II) is proportional to the square of the laser fluence, indicating that the photoreduction of Eu(III) is induced by a two-photon process.

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