Pressure broadening of methane lines in the 6190Åand 6825Åbands at room and low temperatures

Temperature dependence of rotational relaxation of methane in the 2ν3 vibrational state by self- and nitrogen-collisions and comparison with line broadening measurements

“…With our method of direct measurements of the rotational depopulation rates it is possible to obtain the depopulation rate coefficient of a well defined rovibrational level with a selected tetrahedral symmetry species A, E, F whereas, in line width measurements, the determination of the broadening coefficient for each tetrahedral component of a multiplet is not straightforward. Furthermore, for self-collisions, rotational depopulation rates can be measured at low temperature while the pressure above [15] which methane condenses is too low to measure pressure broadening accurately.…”

“…For self-broadening, the only measurements performed at a temperature of 100 K are from Varanasi et al [14] for the R(0), R(1) and R(2) lines in the m 3 band and from Keffer et al [15] for unassigned lines of the 0.619 and 0.682 lm bands. For the R(0) line of m 3 , the self-broadening coefficient at 100 K is found to be (0.20 ± 0.02) cm À1 atm À1 that is close to the value obtained for 2m 3 though the upper vibrational states are different.…”

“…The collisional broadening coefficients have been measured for various CH 4 transitions as a function of temperature for self-or N 2 -broadening [13][14][15][16][17][18][19][20][21]. Most of the data on IR lines have been plotted in Figs.…”

“…For N 2 -broadening, apart from the measurements performed at low temperature for unassigned lines of the 0.619 and 0.682 lm bands [15] or of the 0.727 lm band [16], most of the other temperature-dependence studies relate to the m 4 band [17][18][19][20] but there are no data at temperature lower than 130 K [17]. At this temperature, the lowest J value of m 4 levels in the studied lines is J = 4 that is the upper level of the P(5)E and P(5)F lines.…”

N2-, O2- and air-broadened half-widths and line shifts for transitions in the ν3 band of methane in the 2726- to 3200-cm−1 spectral region

“…There have been numerous half-width measurements for transitions of 12 CH 4 with N 2 [24,[32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]] O 2 , [32,42,44,45,48,49] air [32,36,38,40,42,43,45,[50][51][52][53], CH 4 [32,34,36,39,44,48,49,[54][55][56][57][58][59][60], and other molecules/atoms [32,…”