Raman Studies on Solid CO2 and N2 with Excess He at Pressures up to 40 GPa

A. P. Jephcoat, H. Olijnyk

Research output: Contribution to journalArticle

Abstract

Raman spectra of CO2 and the van-der-Waals compound He(N2)11 were obtained under nearly hydrostatic pressures up to 40 GPa. The pressure induced changes of the librational spectra suggest that solid CO2 does not transform directly from phase-I (cubic Pa3) to phase-Ill (orthorhombic Cmca). An intermediate phase-IV. which may involve only minor modifications of phase-I, is formed prior to the transition to Cmca structure Phases IV and III coexist over some pressure range. The pressure shifts of all four Raman active librons of phase-Ill were determined over a wide pressure range and are compared to previous theoretical results. Spectra of external and internal modes of the van-der-Waals compound He(N2)11 are very similar to those of ε-N2 and imply a close relationship between the structures of He(N2)11 and ε-N2. The observed splitting of the main vibron of isotopic species 14N-15N indicates that in addition to factor-group interactions site effects are responsible for the observed splittings of the 14N2 main vibron of He(N2)11.

Original languageEnglish
Pages (from-to)121-123
Number of pages3
JournalReview of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu
Volume8
Issue number2
DOIs
Publication statusPublished - 1998
Externally publishedYes

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trucks
overpressure
hydrostatic pressure
Hydrostatic pressure
Phase structure
Raman spectra
Raman scattering
shift
interactions

Keywords

  • high pressure
  • molecular crystals
  • phase transitions
  • vibrational spectroscopy

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Raman Studies on Solid CO2 and N2 with Excess He at Pressures up to 40 GPa. / Jephcoat, A. P.; Olijnyk, H.

In: Review of High Pressure Science and Technology/Koatsuryoku No Kagaku To Gijutsu, Vol. 8, No. 2, 1998, p. 121-123.

Research output: Contribution to journalArticle

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AB - Raman spectra of CO2 and the van-der-Waals compound He(N2)11 were obtained under nearly hydrostatic pressures up to 40 GPa. The pressure induced changes of the librational spectra suggest that solid CO2 does not transform directly from phase-I (cubic Pa3) to phase-Ill (orthorhombic Cmca). An intermediate phase-IV. which may involve only minor modifications of phase-I, is formed prior to the transition to Cmca structure Phases IV and III coexist over some pressure range. The pressure shifts of all four Raman active librons of phase-Ill were determined over a wide pressure range and are compared to previous theoretical results. Spectra of external and internal modes of the van-der-Waals compound He(N2)11 are very similar to those of ε-N2 and imply a close relationship between the structures of He(N2)11 and ε-N2. The observed splitting of the main vibron of isotopic species 14N-15N indicates that in addition to factor-group interactions site effects are responsible for the observed splittings of the 14N2 main vibron of He(N2)11.

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