Atmospheric absorption of 10.6-mu radiation can either heat or cool the air, depending upon atmospheric conditions. Absorption by CO(2) is essentially from the (100) to the (001) states. The depleted (100) state is rapidly replenished by energy transfer from translation, cooling the atmosphere. The (001) state slowly transfers energy through the N(2) back to translation, eventually heating the atmosphere. Cooling increases the density and index of refraction, and the resulting gradient tends to focus a gaussian beam. This partially offsets the usual heating effects and associated ray divergence.

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Selective OD bond dissociation of HOD: Photodissociation of vibrationally excited HOD in the 5 O D statePhotoacoustic measurements of the vibrational relaxation of the selectively excited ozone ( 3 ) molecule in pure ozone and its binary mixtures with O 2 ,N 2 , and noble gasesThe rate constants associated with the deactivation of vibrationally excited CO 2 *(P3) by collision with either CO2 or N2 have been experimentally determined from 300 o -1000oK by a laser fluorescence method. The reactions investigated were k.where the asterisk denotes a vibrationally excited molecule, and the quantities in parentheses represent the specific excited modes of CO2. The rate constant k6 varies with temperature T (OK) as 8.60X10 7 jP/2 torr-I. sec-I. From 4OO o -1000oK the rate constant kl (per torr-I 'second-I ) varies with temperature aswith A = 6.79 and B = 30.8. From 300°-4QOoK the measured values of kl are greater than those corresponding to the above relation. The rate constant k6 increases from a value of 110 torr-I'sec l at room temperature to a value of 2700 torr-I. sec-1 at 1000oK, but the variation of k& with temperature cannot be simply expressed. The rate constant kl was found to be negligibly small compared to the other rate constants.

The use of Thomson scattering of a laser beam as a diagnostic technique for laboratory plasmas is discussed. Several potential sources of difficulty in the use of this technique are investigated. Included are simple signal-to-noise considerations based upon photon counting statistics and noise due to plasma radiation, Rayleigh or Raman scattering from neutral particles in the plasma, and scattering from walls, apertures, etc. in the apparatus. Also discussed are other effects which may affect the state of the plasma being measured, namely, free-free absorption which leads to electron heating and free-bound absorption or photo-ionization which can produce additional electrons. Experimental determinations of electron density and temperature in a steady-state hollow-cathode arc plasma, by Thomson scattering of a ruby laser beam, are reported and discussed. These measurements refer primarily to argon plasmas over an electron density range 1013–1014 cm−3 and electron temperature range 3–8 eV. Essential agreement of these measurements with measurements of the same quantities by Langmuir probes is obtained, except for some interesting explainable differences.

The rate constants associated with the deactivation of vibrationally excited CO2*(001) by collisions with CO have been experimentally determined from 300 to 900°K by a laser fluorescence method. These reactions involving CO considered were CO2*(001)+CO⇆ lim k2k1CO2+CO*(υ = 1), CO2*(001)+CO→ lim kCOCO2(ν1, ν2)+CO, CO*(υ = 1)+CO2→ lim k4CO+CO2(ν1, ν2), where CO2(ν1, ν2) is an unidentified product state. Within experimental error the rate constant k1 increases linearly with temperature T(°K) from a value of 5.7 × 103 torr−1·sec−1 at room temperature to a value of 11.2 × 103 torr−1·sec−1 at 900°K. From 500 to 900°K the rate constant kCO(torr−1·seconds−1) varies with temperature as log10kCO = A − BT−1/3, with A = 6.61 and B = 31.6. From 300 to 500°K the measured values of kCO are greater than those corresponding to the cited relation. The rate constant k4 was found to be negligible compared to kCO. The probability per collision of vibrational energy transfer from CO2*(001) to CO(υ = 0) was computed by a theory involving long range forces. The calculated probabilities, using only multipolar interaction and only exponential repulsive interaction, are in equally good agreement with the probabilities deduced from measurement of R1, the transfer rate constant in the exothermic direction.