TY  - JOUR
A1  - Sublett, David Matthew
A1  - Sendula, Eszter
A1  - Lamadrid, Hector
A1  - Steele-MacInnis, Matthew
A1  - Spiekermann, Georg
A1  - Burruss, Robert C.
A1  - Bodnar, Robert J.
T1  - Shift in the Raman symmetric stretching band of N-2, CO2, and CH4 as a function of temperature, pressure, and density
JF  - Journal of Raman spectroscopy : JRS
N2  - The Raman spectra of pure N-2, CO2, and CH4 were analyzed over the range 10 to 500 bars and from -160 degrees C to 200 degrees C (N-2), 22 degrees C to 350 degrees C (CO2), and -100 degrees C to 450 degrees C (CH4). At constant temperature, Raman peak position, including the more intense CO2 peak (nu+), decreases (shifts to lower wave number) with increasing pressure for all three gases over the entire pressure and temperature (PT) range studied. At constant pressure, the peak position for CO2 and CH4 increases (shifts to higher wave number) with increasing temperature over the entire PT range studied. In contrast, N-2 first shows an increase in peak position with increasing temperature at constant pressure, followed by a decrease in peak position with increasing temperature. The inflection temperature at which the trend reverses for N-2 is located between 0 degrees C and 50 degrees C at pressures above similar to 50 bars and is pressure dependent. Below similar to 50 bars, the inflection temperature was observed as low as -120 degrees C. The shifts in Raman peak positions with PT are related to relative density changes, which reflect changes in intermolecular attraction and repulsion. A conceptual model relating the Raman spectral properties of N-2, CO2, and CH4 to relative density (volume) changes and attractive and repulsive forces is presented here. Additionally, reduced temperature-dependent densimeters and barometers are presented for each pure component over the respective PT ranges. The Raman spectral behavior of the pure gases as a function of temperature and pressure is assessed to provide a framework for understanding the behavior of each component in multicomponent N-2-CO2-CH4 gas systems in a future study.
KW  - fluids
KW  - wave number
KW  - attraction
KW  - repulsion
Y1  - 2019
U6  - https://doi.org/10.1002/jrs.5805
SN  - 0377-0486
SN  - 1097-4555
VL  - 51
IS  - 3
SP  - 555
EP  - 568
PB  - Wiley
CY  - Hoboken
ER  -