Thermal Relaxation in Oxygen with H2O, HDO, and D2O Vapors as Impurities

Abstract

Using the 100% relative-humidity technique for controlling the mole fraction of water vapor, the Napier (relaxation) frequency of oxygen has been measured as a function of the mole fraction of various water vapors, consisting of pure H20, pure D20, and three mixtures thereof. Pure H20 gives, as is well known, a quadratic in H, the mole fraction; pure D•O gives a linear relation down to 0.7X 10 -a. The mixtures show a linear relation above 1.5 X 10-a and a curvilinear approach to zero below that. Calculation indicates that the heterogeneous molecule HDO is far more effective as a thermal equilibrator for oxygen than either of its homogeneous parents. Quantitatively, with (f/p),,, in cps per atm and h in mole fraction X 10 a, the results are-100% H•O' (f/p),,,= 7 q-183hq-132h•-; 50% D•O' (f/p),•=--664q-llOOh; 80% D20' (f/p),•= --490q-908h; 92% D20' (f/p),,,= --250q-585h (above h= 1.3); 92% D•O' (f/p),•= 7q-275hq-100h•(below h= 1.3); 99.8% D•.O' (f/p),•=--85q-385h.

Vibrational Energy Transfer and Relaxation in O2and H2O

“…where Under the assumption that [O 2 (0)] and [H 2 O(000)] can be taken to be time independent (i.e., that the effective vibrational temperatures are not too high), we can take α, β, γ, and δ as constants for any specific experiment, and then we solve the differential equations analytically, obtaining where λ(fast) and λ(slow) are calculated from the two roots of the eigenvalue equation resulting in A similar analysis is provided by Henderson et al A more complete description would include the expected thermal equilibrium values of [O 2 (1)] and [H 2 O(010)], but the conclusions derived here about time dependence would be unchanged. The time dependencies of both [O 2 (1)] and [H 2 O(010)] are thus described by double exponentials, with an initially excited level decaying at first fast and then slow, while an initally unexcited level would rise quickly and decay slowly, as reflected in the coefficients A − D as defined by the initial excitation conditions.…”

“…As a result, much more complicated modeling would be required to extract reliable rate coefficients from experiments of the type performed previously. Henderson et al 35 and Monk 36 show that the decay rates observed in sound absorption vary quadratically in the water mole fraction below 1%.…”

Remote sensing of the troposphere

“…As a result, the percentage of O2 molecules, excited by the compression of sound waves into the first vibrational level, which remain in the excited state, may then collide with HO molecules and transfer their energy into the 010 vibrational state of HO, effectively heating the H20 by this resonant exchange. The interchange of energy is quite rapid (Henderson, Clark, Lintz, 1965).…”