Low Temperature Physics: 29, 801 (2003); https://doi.org/10.1063/1.1614197 (4 pages)
Физика Низких Температур: Том 29, Выпуск 9-10 (Сентябрь 2003), c. 1057-1060    ( к оглавлению , назад )

Molecular probing of low-temperature incommensurate phases

J. Kikas

Institute of Materials Science, University of Tartu, 4 Tähe, Tartu 51010, Estonia
E-mail: jaakk@physic.ut.ee

A. Suisalu, A. Laisaar, and An. Kuznetsov

Institute of Physics, University of Tartu, 142 Riia, Tartu 51014, Estonia

Аннотация

Two-dimensional (2D) excitation-emission spectra of biphenyl doped with free-base chlorin were measured at 5 K under various pressures up to 350 MPa. Besides the features related to zero-phonon lines and their phonon sidebands, a broad spectral band amounting to 80% of the total intensity at 5 K was revealed in the 2D spectra. The obtained inhomogeneous distribution function shows drastic changes with increasing pressure — the triplet structure observable at normal pressure in the incommensurate phase ICIII of biphenyl converges to a singlet in the high-pressure commensurate phase CI. These observations are assumed to reflect specific for incommensurate phases relaxation after an optical excitation of probe molecules and interaction of them with the incommensurate modulation wave.

PACS:
61.44.Fw - Incommensurate crystals
62.50.+p - High-pressure and shock wave effects in solids and liquids (for high pressure apparatus and techniques, see 07.35.+k; for shock wave initiated high-pressure chemistry, see 82.40.Fp; for high-pressure behavior of rocks and minerals, see 91.60.Gf; see also
64.70.Rh - Commensurate-incommensurate transitions
78.55.Kz - Solid organic materials