Raman Studies on Solid CO_2 and N_2 with Excess He at Pressures up to 40 GPa
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Raman spectra of CO<SUB>2</SUB> and the van-der-Waals compound He (N<SUB>2</SUB>) <SUB>11</SUB> were obtained under nearly hydrostatic pressures up to 40 GPa. The pressure induced changes of the librational spectra suggest that solid CO<SUB>2</SUB> does not transform directly from phase-I (cubic Pa<SUB>3</SUB>) to phase-III (orthorhombic Cmca). An intermediate phase-IV. which may involve only minor modifications of phase-I, is formed prior to the transition to Cmca structure. P hases IV and III coexist over some pressure range. The pressure shifts of all four Raman active librons of phase-III 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 (N<SUB>2</SUB>) <SUB>11</SUB> are very similar to those of ε-N<SUB>2</SUB> and imply a close relationship between the structures of He (N<SUB>2</SUB>) <SUB>11</SUB> and ε-N<SUB>2</SUB>. The observed splitting of the main vibron of isotopic species <SUP>14</SUP>N-<SUP>15</SUP>N indicates that in addition to factor-group interactions site effects are responsible for the observed splittings of the <SUP>14</SUP>N<SUB>2</SUB> main vibron of He (N<SUB>2</SUB>) <SUB>11</SUB>.
- The Review of High Pressure Science and Technology
The Review of High Pressure Science and Technology 8(2), 121-123, 1998-05-20
The Japan Society of High Pressure Science and Technology