title: Structural study of the thermally induced and photoinduced phase transitions of the 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) radical.
abstract: We report on the first direct atomic-level photodiffraction evidence for domain formation by doping with charge photocarriers of the stable organic radical TTTA (1,3,5-trithia-2,4,6-triazapentalenyl), which exhibits unusually wide thermal hysteresis of the paramagnetic-to-diamagnetic phase transition around ambient temperature. A setup for steady-state powder photodiffraction was developed for the purpose, composed of a second harmonic pulsed visible pump (532 nm) coupled with a powder diffractometer using monochromatic synchrotron X-ray radiation as the probe. The refined structures of the photoinduced phase and the high-temperature phase are structurally identical. The result supports the model according to which photoexcitation causes suppression of the spin-Peierls instability and separation of the radical dimers, resulting in a structure that is essentially identical with the unperturbed high-temperature phase.
authors.affiliation: International Center for Young Scientists, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan. naumov.pance@nims.go.jp
authors.forename: Pance
authors.initials: P
authors.lastname: Naumov
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Hill
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakurai
authors.forename: Masahiko
authors.initials: M
authors.lastname: Tanaka
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Ariga