title: Temperature dependent absorption spectra of Br(-), Br2(•-), and Br3(-) in aqueous solutions.
abstract: The absorption spectra of Br(2)(•-) and Br(3)(-) in aqueous solutions are investigated by pulse radiolysis techniques from room temperature to 380 and 350 °C, respectively. Br(2)(•-) can be observed even in supercritical conditions, showing that this species could be used as a probe in pulse radiolysis at high temperature and even under supercritical conditions. The weak temperature effect on the absorption spectra of Br(2)(•-) and Br(3)(-) is because, in these two systems, the transition occurs between two valence states; for example, for Br(2)(-) we have (2)Σ(u) → (2)Σ(g) transition. These valence transitions involve no diffuse final state. However, the absorption band of Br(-) undergoes an important red shift to longer wavelengths. We performed classical dynamics of hydrated Br(-) system at 20 and 300 °C under pressure of 25 MPa. The radial distribution functions (rdf's) show that the strong temperature increase (from 20 to 300 °C) does not change the radius of the solvent first shell. On the other hand, it shifts dramatically (by 1 Å) the second maximum of the Br-O rdf and introduces much disorder. This shows that the first water shell is strongly bound to the anion whatever the temperature. The first two water shells form a cavity of a roughly spherical shape around the anion. By TDDFT method, we calculated the absorption spectra of hydrated Br(-) at two temperatures and we compared the results with the experimental data.
authors.affiliation: Nuclear Engineering and Science Directorate, Japan Atomic Energy Agency, Nakagun, Ibaraki, Japan.
authors.forename: Mingzhang
authors.initials: M
authors.lastname: Lin
authors.forename: Pierre
authors.initials: P
authors.lastname: Archirel
authors.forename: Nguyen Thi
authors.initials: NT
authors.lastname: Van-Oanh
authors.forename: Yusa
authors.initials: Y
authors.lastname: Muroya
authors.forename: Haiying
authors.initials: H
authors.lastname: Fu
authors.forename: Yu
authors.initials: Y
authors.lastname: Yan
authors.forename: Ryuji
authors.initials: R
authors.lastname: Nagaishi
authors.forename: Yuta
authors.initials: Y
authors.lastname: Kumagai
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Katsumura
authors.forename: Mehran
authors.initials: M
authors.lastname: Mostafavi