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Collision-induced Absorption in Gases (Cambridge Monographs by Lothar Frommhold

By Lothar Frommhold

The ebook reports our current wisdom of collision-induced absorption of infrared radiation in dense gases. The ebook starts off with a recapitulation of crucial heritage info. Experimental effects for the absorption spectra are subsequent mentioned. Then the factors and homes of dipole moments brought on by means of molecular interactions are reviewed. following chapters current the speculation of collision-induced absorption in monatomic fuel combos and in molecular gases and combinations. the ultimate bankruptcy discusses similar phenomena and critical purposes in astrophysics. The publication is a pragmatic consultant for the spectroscopic facing dense, impartial fluids.

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11) For rough estimates, the collisional cross section may be assumed to be velocity-independent, 612(^12) = 2o = constant (hard-sphere approximation), so that the mean time between collisions becomes T12 = VT21 = (vn n2 Qo)'1 with v12 = [SkT/(nml2)]1/2 . 12) The average speed is obtained with the assumption of a Maxwellian velocity distribution. The average relative speed of a collisional pair 1-2 is of the order of the root-mean-square speed, which is roughly equal to the speed of sound and varies with temperature as T" 1 / 2 .

At low pressures and/or high temperatures, especially for the lighter gases, the free-particle expressions, Eq. 4 Distribution functions The probability that two atoms 1,2 are separated by the distance R is given by the pair distribution function, g(l2\R), defined as with R = R2 — Ru R = \R\; the q\9 q2, are the laboratory position coordinates of atoms 1 and 2. 3 — R\; 9 is the angle subtended by the vectors R and Rf. The virial expansions of these distribution functions [135] are given by g(12) (R) = g f \R) + n, gjifW + n2 ggf (*) + ...

86 may be considered the Schrodinger representation of the absorption of radiation by quantum systems in terms of spectroscopic transitions between states |i) and | / ) .

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