TY - JOUR
T1 - Coherent anti-Stokes Raman scattering spectroscopy of solid nitrogen to 22 GPa
AU - Hellwig, H
AU - Daniels, WB
AU - Hemley, RJ
AU - Mao, HK
AU - Gregoryanz, E
AU - Yu, ZH
PY - 2001/12/15
Y1 - 2001/12/15
N2 - The Raman-active vibron modes of solid nitrogen have been investigated by coherent anti-Stokes Raman scattering (CARS) spectroscopy to 22 GPa at room temperature. Frequencies and linewidths were measured with an accuracy of 0.1 to 0.2 cm(-1). From the pressure dependence of the linewidths a dynamical model for the transitions between the delta, delta (loc), and epsilon phases has been developed. These phase transitions are characterized by different degrees of ordering of the N(2) molecules. The processes can be described by an increase in the orientational order with increasing pressure and a decrease in number in the rotational degrees of freedom at the phase transitions coupled with changes in crystal structure. A structural model for the delta (loc) phase is given, in which the delta-delta (loc)-epsilon transition sequence arises from a group/subgroup relationship and can therefore be considered ferroelastic in nature. Sample annealing was found to have a significant effect on the results. (C) 2001 American Institute of Physics.
AB - The Raman-active vibron modes of solid nitrogen have been investigated by coherent anti-Stokes Raman scattering (CARS) spectroscopy to 22 GPa at room temperature. Frequencies and linewidths were measured with an accuracy of 0.1 to 0.2 cm(-1). From the pressure dependence of the linewidths a dynamical model for the transitions between the delta, delta (loc), and epsilon phases has been developed. These phase transitions are characterized by different degrees of ordering of the N(2) molecules. The processes can be described by an increase in the orientational order with increasing pressure and a decrease in number in the rotational degrees of freedom at the phase transitions coupled with changes in crystal structure. A structural model for the delta (loc) phase is given, in which the delta-delta (loc)-epsilon transition sequence arises from a group/subgroup relationship and can therefore be considered ferroelastic in nature. Sample annealing was found to have a significant effect on the results. (C) 2001 American Institute of Physics.
KW - X-RAY-DIFFRACTION
KW - HIGH-PRESSURE PHASES
KW - N-2
KW - TEMPERATURE
KW - SPECTRUM
KW - BEHAVIOR
KW - 300-K
KW - N2
M3 - Article
VL - 115
SP - 10876
EP - 10882
JO - The Journal of Chemical Physics
T2 - The Journal of Chemical Physics
JF - The Journal of Chemical Physics
SN - 0021-9606
IS - 23
ER -