NO in the Upper Atmosphere

The ionization of NO by the Lyman-a line is the main source of ions in the D region. The photodissociation of NO in the upper atmosphere occurs from the /t2Z + (F > 4), B2n (c > 7), and C2n (F > 0). The dissociation rate of NO by the solar radiation is proportional to the integrated absorption coefficient of various bands (that is, the oscillator strength). From Table V 4 it can be seen that absorption by the /if (12,0) and 6 bands is most important in leading to photodissociation. 

Photo-ionization of nitrous oxide in the upper atmosphere only occurs with light of wavelengths shorter than 134 nm, to cause the reaction NO + /7v - NO+ + e-. 

Ozone is the fourth strongest oxidant known to man and is more effective at sterilizing water than chlorine. Ozone s reaction with NO is a natural phenomenon that takes place in the upper atmosphere that depletes the ozone layer and creates acid... 

The production of NOz, with NO as a possible precursor to NOz, has been observed when synthetic air or 02/N2 mixtures are photolyzed using a deuterium lamp, an argon flash lamp, or a 185-nm mercury line (Zipf and Prasad, 1998a). They proposed that this occurs from the reaction of electronically excited 02(B%) with N2, or photodissociation of 02 N2 dimer, and that the rate of NOx production from this process could be comparable to that from reaction (13b) (Zipf and Prasad, 1998a Prasad, 1998). If this proves to be the case, there must be some unidentified NOx sinks to be consistent with the measured NOx concentrations in the upper atmosphere. 

Though most of the oxygen in the atmosphere has been formed by photosynthesis in plants, some is produced by photolysis of water vapour in the vacuum ultraviolet region A <200 nm. Photolysis of N2, NO, N02, NHa, CO, 002 and small aliphatic hydrocarbons (alkanes) set up complex reactions in the upper atmosphere. 

Nitric oxide is also present in the upper atmosphere its role has been reviewed by Nicolet.326-328 Because of solar radiation, important processes are photoionization, photodissociation, and the formation of electronically excited levels. The continuum seen in the night airglow has often been ascribed to reaction (4). However, both the y and / bands of NO are absent in the night airglow. Since the / and y emissions arise from... 

Because of its low ionization potential, NO+ is a relatively easily formed ion and can be produced by charge transfer to NO. Thus, this ion is an important one, both in the upper atmosphere and in ballistic missile reentry wakes. 

Plwtodissociatiqn of 02 in the Upper Atmosphere. The source of O atoms above an altitude of 50 km is mainly from the photolysis of 02 in the Herzberg I and Schumann-Runge continua (488). The predissociation of 02 in the Schumann Runge bands (r > 3) [Wray and Fried (1054)] is the additional source of O atoms between 65 and 95 km. Supporting evidence of the predissoeiation is that no fluorescence of the Schumann-Runge bands above v > 1 has been observed in the upper atmosphere. 

The possibility of deactivation of vibrationally excited molecules by spontaneous radiation is always present for infrared-active vibrational modes, but this is usually much slower than collisional deactivation and plays no significant role (this is obviously not the case for infrared gas lasers). CO is a particular exception in possessing an infrared-active vibration of high frequency (2144 cm-1). The probability of spontaneous emission depends on the cube of the frequency, so that the radiative life decreases as the third power of the frequency, and is, of course, independent of both pressure and temperature the collisional life, in contrast, increases exponentially with the frequency. Reference to the vibrational relaxation times given in Table 2, where CO has the highest vibrational frequency and shortest radiative lifetime of the polar molecules listed, shows that most vibrational relaxation times are much shorter than the 3 x 104 /isec radiative lifetime of CO. For CO itself radiative deactivation only becomes important at lower temperatures, where collisional deactivation is very slow indeed, and the specific heat contribution of vibrational energy is infinitesimal. Radiative processes do play an important role in reactions in the upper atmosphere, where collision rates are extremely slow. 

In view of the very close agreement between the matrix isolation visible absorption spectra of the HAIOH molecule and the chemiluminescence features observed in the gas-phase oxidation of aluminum in the upper atmosphere (14) and in the laboratory ( ), this study further substantiates the plausibility that the continuum emitter is the divalent oxidative insertion product of a 1 1 alumlmmi hydration reaction, HAIOH. The Insertion reaction is probably facile however, it is possible that radiation from the furnaces may have photolyzed the AI...OH2 adduct to the insertion product during co-condensation. Preliminary theoretical studies indicate there is no potential energy barrier in going directly to the Insertion product from A1 + H2O ( ). 

---