Foreign-gas collision broadening of the far-infrared spectrum of water vapor

Collisional-Broadened and Dicke-Narrowed Lineshapes of H216O and H218O Transitions at 1.39 μm

“…That is also in agreement with the results found by the authors of Ref. (33), which found C b (N 2 )/C b (O 2 ) ϭ 1.6(3) and those of the Ref. (24), which also found C b (N 2 )/C b (O 2 ) to vary in the range between 1.65(6) and 1.74 (8).…”

“…(33) for transitions in the microwave region and by Grossman and Browell for the 3 1 ϩ 3 and 2 1 ϩ 3 bands (23, 24), we observed that the nitrogen perturber was more effective than oxygen. In column five of Table 2, we report the experimental and theoretical ratios between the broadening coefficients for nitrogen and oxygen.…”

“…Differences in the collisional rate of nitrogen and oxygen are probably due to their different quadrupole moments, Q, which play an important role in the dipole-quadrupole interaction occurring in the collision between H 2 O and N 2 or O 2 molecules. Indeed, the quadrupole moment of these molecules is Q N2 ϭ Ϫ3.04 ϫ 10 Ϫ26 esu cm and Q O2 ϭ Ϫ0.78 ϫ 10 Ϫ26 esu cm 2 (33), while their ratio, Q N2 /Q O2 , is 3.9. This value, of course, cannot be directly compared with the ratio of the broadening coefficients since the dependence on quadrupole moments occurs in a nontrivial way in the RB theory.…”

Numerical removal of water vapour effects from terahertz time-domain spectroscopy measurements

“…More specifically, the collision broadened linewidth is dependent on pressure (Bernath 2005) and temperature (Gasster et al 1988;Cheville & Grischkowsky 1999;Podobedov et al 2004). This dependency yields the Benedict & Kaplan relationship (Benedict & Kaplan 1964;Kemp et al 1978),…”

Self-, Nitrogen-, and Oxygen-Broadening Coefficient Measurements in the ν1 Band of H2O Using a Difference Frequency Generation Spectrometer at 3 μm

“…From our values we found γ N 2 /γ O 2 exp = 1.6(4), while from the Delaye data γ N 2 /γ O 2 th = 1.6(2), which are in very good agreement, although the line-by-line differences between the experimental and theoretical ratio are quit significant. Moreover, it is worth to note that both the work of Gasster et al (10) and that of Grossmann and Browell (12) provide for γ N 2 /γ O 2 the values of 1.64(29) and 1.674(75), respectively. In addition also in our recent investigation concerning ν 1 + ν 3 lines (18) we obtained a ratio varying between 1.57 and 2.40.…”