Role of diffusion in the violation of the long‐wave approximation in line wings

Abstract

The asymptotic line wing theory assumes the presence of two intermolecular interaction characteristics–quantum and classical intermolecular interaction potentials–in the expression of the absorption coefficient. The same classical potential enters into the expression for the second virial coefficient. The classical potential found from the second virial coefficient data is used for calculating of the temperature dependence of the absorption coefficient of water vapor line wings in the 8–12 μm transparency window. To obtain agreement between the calculated and experimental absorption coefficients at this point, it is necessary to refine the expression for the absorption coefficient by abandoning the longwave approximation in line wings. The calculation that meets this condition is performed in the framework of a diffusion model. The time between collisions of certain type giving rise to line wing absorption is estimated. © 2012 Wiley Periodicals, Inc.

A description of the H2O absorption in the 3−5 μm spectral region in violation of the long-wave approximation in line wings

“…We have used a simplified molecular evolution model for the radiation absorption with large frequency detunings to calculate the absorption coefficient, taking into account violation of the long-wave approximation for molecular centers of mass. The model reduces the molecular evolution to a diffusion process and relies on the intercollision time of a given type (the drift time) 1,3 . The use of the model gives rise to an additional factor d K in the absorption coefficient:…”

Spectral line shape and absorption in atmospheric windows

“…Îñíîâíûì ïðèáëèaeåíèåì, èñïîëüçîâàííûì ïðè âûâîäå âûðàaeåíèÿ (27), ÿâëÿåòñÿ íàëè÷èå áîëüøèõ ñìåùåííûõ ÷àñòîò (21). Íà ýòîì aeå óñëîâèè îñíîâàíà è àñèìïòîòè÷åñêàÿ îöåíêà èíòåãðàëà ïî âðåìåíè â (24). Ïî-âèäèìîìó, (27) åñòü ìàêñèìóì òîãî, ÷òî ìîaeåò áûòü äîñòèãíóòî, èñõîäÿ èç îáùèõ ïðèíöèïîâ, ïðè îïèñàíèè êîýôôèöèåíòà ïîãëîùåíèÿ íà áîëüøèõ ñìåùåííûõ ÷àñòîòàõ.…”

“…Ïîëíîå ìàòåìàòè÷åñêîå ðåøåíèå ýòîé ïðîáëåìû ðàñ÷åòà êîýôôèöèåíòà ïîãëîùåíèÿ ïðè íàðóøåíèè äëèííîâîëíîâîãî ïðèáëèaeåíèÿ äëÿ öåíòðîâ ìàññ ìîëåêóë åùå ïðåäñòîèò íàéòè. Ìû èñïîëüçîâàëè äëÿ ðàñ÷åòà êîýôôèöèåíòà ïîãëîùåíèÿ ñ ó÷åòîì íàðóøåíèÿ äëèííîâîëíîâîãî ïðèáëèaeåíèÿ äëÿ öåíòðîâ ìàññ ìîëåêóë óïðîùåííóþ ìîäåëü ýâîëþöèè ìîëåêóëû ïðè ïîãëîùåíèè èçëó÷åíèÿ ñ áîëüøîé ñìåùåííîé ÷àñòîòîé, êîòîðàÿ ñâîäèò ýòó ýâîëþöèþ ê ïðîöåññó äèôôóçèè è îïåðèðóåò âðåìåíåì ìåaeäó ñòîëêíîâåíèÿìè îïðåäåëåííîãî òèïà (âðåìåíåì äðåéôà) [3,24]. Ïðèìåíåíèå ìîäåëè ïðèâîäèò ê ïîÿâëåíèþ äîïîëíèòåëüíîãî ìíîaeèòåëÿ K d â êîýôôèöèåíòå ïîãëîùåíèÿ:…”

“…Âûõîä áûë íàéäåí íà ïóòè îòêàçà îò äëèííîâîëíîâîãî ïðèáëèaeåíèÿ äëÿ öåíòðîâ ìàññ ìîëåêóë. Ýòîò âàðèàíò àñèìïòîòè÷åñêîé òåîðèè êðûëüåâ ëèíèé áûë èñïîëüçîâàí â ðàñ÷åòå êîíòèíóàëüíîãî ïîãëîùåíèÿ âîäÿíûì ïàðîì äëÿ èíòåðâàëîâ 8-12 [24] è 3-5 ìêì [53].…”