Izvorni znanstveni članak
Asymmetric profile of the totally symmetric stretching band in Raman spectra of bis(trimethylsilyl)acetylene
Vlaste Mohačel-Grošev
; Ruđer Bošković Institute, POB 180, 10002 Zagreb, Croatia
Krešimir Furić
; Ruđer Bošković Institute, POB 180, 10002 Zagreb, Croatia
Sažetak
The asymmetric band profile of the triple C = C stretching Raman band in bis(trimethylsilyl)acetylene was decomposed into a higher and a lower wavenumber part, each described as one half of a Lorentzian bandshape with its own halfwidth (Γhigh and Γlow), but with common band centre and maximum point. Γhigh and Γlow were fitted at seventeen different temperatures ranging from 110 K to 323 K (the melting point occurring roughly at 290 K). It was found that lower wavenumber side of the band was considerably broader than the higher wavenumber side, throughout the whole temperature interval chosen. This unexpected crystal-band asymmetry, present together with the ”normal” phonon spectrum, seems to indicate a freezing of orientational disorder of methyl groups, while molecular centres of mass remain positioned on the Bravais lattice – like in the case of the so called glassy crystals. The asymmetry of the band above 290 K suggests the existence of a nonisotropic liquid state.
Ključne riječi
Raman spectra; bis(trimethylsilyl)acetylene; low temperature; disorder; glassy crystal
Hrčak ID:
302003
URI
Datum izdavanja:
1.5.2005.
Posjeta: 181 *