CO2–CO2 and CO2–Ar continua at millimeter wavelengths

Pure rotational R(0) and R(1) lines of CO in Ar baths: experimental broadening, shifting and mixing parameters in a wide pressure range versus ab initio calculations

“…Such a behavior of the continuum in the millimeter-wave range was demonstrated for many molecular systems ( e.g. , H 2 O–N 2 , 56 N 2 –N 2 , 57 CO 2 –CO 2 and CO 2 –Ar 58 ). This quadratic growth is a general property of matter stipulated by the frequency dependence of the so-called radiation term (see, e.g.…”

“…The same has been proved for CO 2 –CO 2 and even CO 2 –Ar pairs. 11–13 However, the free pair component is dominating for the N 2 –N 2 continuum and the dimeric part is negligible. 14 The contribution of resonant line wings to the continuum remains one of the oldest unsolved problems in molecular spectroscopy.…”

On the nature of sub-THz continuum absorption in CO2 gas, its mixture with Ar, and in pure water vapor

“…The continuum absorption spectra were investigated following the approach used in our previous works. 19,20 The absorption coefficient α ( f ) was obtained with a resonator spectrometer, 47,48 the operating principle of which is based on measuring changes in the resonance curve width of a high-finesse (quality factor Q = f /Δ f ∼ 10 6 ) Fabry–Perot resonator filled with absorbing gas:where f is the resonance frequency, c is the speed of light, Δ f and Δ f 0 are the widths of the resonance curve when the resonator is filled with the investigated (absorbing) and non-absorbing gases, respectively. Absorption measurements are carried out at TEM00q frequencies of the cavity modes separated from each other by approximately 300 MHz.…”

“…Satisfactory agreement between calculated and measured collision-induced spectra was reached using CTS in a series of simulations for various polyatomic systems, such as N 2 –N 2 , CO 2 –Ar, CH 4 –N 2 . 16–21 Note, however, that both classical methods, CMDS and CTS, have to cautiously incorporate an approximate quantum correction to the spectral profile owed to the detailed balance principle. 22…”

Increase of Radiative Forcing through Midinfrared Absorption by Stable CO2 Dimers?

“… 9 However, dimerization may also result in stable dimers (or tightly bound dimers), which have been recently considered in broad-band spectra. 10 In the mid-IR, such stable dimers would lead to permanent additional absorptions in the vicinity of the monomer’s IR absorption. Those additional IR bands are usually hard to distinguish from the rotational–vibrational spectrum of the pure monomer.…”