THE UNIVERSITY OF MICHIGAN COLLEGE OF ENGINEERING Department of Aerospace Engineering High Altitude Engineering Laboratory Scientific Report DISTRIBUTIONS AND LIFETIMES OF N AND NO BETWEEN 100 AND 280 Km S. N. Ghosh ORA Project 05627 under contract with: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CONTRACT NO. NASr-54(05) WASHINGTON, D.C. administered through: OFFICE OF RESEARCH ADMINITSTRATION ANN ARBOR March 1967

'I cI7, i - "

TABLE OF CONTENTS Page LIST OF TABLES v LIST OF FIGURES vii ABSTRACT ix 1. INTRODUCTION 1 2. COMPUTATION OF N AND NO DISTRIBUTIONS AND LIFETIMES 3 3. CONCLUSIONS 11 REFERENCES 15 iii

LIST OF TABLES Table Page 1. Reactions Leading to N-Atom Production and Their Rate Co- 4 efficient 2. Reactions Leading to N-Atom Loss and Their Rate Coefficients 3. Reactions Leading to NO Production and Their Rate Coefficients 6 4. Reactions Leading to NO Loss and Their Rate Coefficients 7 5. Altitude Distributions of Ions 8 6. Lifetimes of N and NO 10 v

LIST OF FIGURES Figure Page 1. Variations of assumed ion densities with altitude. Solid curves are obtained from rocket-borne experiments. The broken curves are extrapolated (see Table 5). 18 2. Production rates of N atoms by various reactions for rate coefficients at laboratory temperature (300~K) assumed constant for the whole altitude range. 19 3. Variation of x with altitude for rate coefficients at laboratory temperature (3000K) assumed constant for the whole altitude range. To obtain loss rate of N atoms, multiply x by [N]. 20 4. Variation of x' with altitude for reactions involving 2 nitrogen atoms. To obtain loss rate multiply x' by [N]2. Loss rates by three-body reactions are very small compared with those for two-body reactions. 21 5. Production rates of N atoms by various reactions for rate coefficients varying with temperature. 22 6. Variation of x with altitude for two-body reactions having rate coefficients varying with temperature. Loss rate = x[N]. NO(i) and NO(4) represent NO density obtained from Curves (1) and (4) of Fig. 9, respectively. 23 7. Production rates of NO molecules by various reactions with rate coefficients varying with temperature. 24 8. Variation of x with altitude for various reactions having rate coefficients varying with temperature. To obtain loss rate of NO molecules, multiply x by [NO]. 25 9. Computed altitude distributions of N and NO. For comparison, the distributions of 0, 02 and N2 obtained from CIRA 1965 are also shown. 26 vii

ABSTRACT The distribution of N atoms between the altitude range 100 and 280 km has been computed from reactions between constituent particles of the atmosphere and assuming their rate coefficients at laboratory temperature (3000K) to be constant for the whole altitude range. It is also calculated for rate coefficients varying with temperature. It has been found that the latter distribution, which is considerably different from the former, gives a reasonably good profile. Since in many cases, reactions involving loss of N-atoms lead to the production of NO molecules, the altitude distribution of NO molecules is also calculated. The computed N and NO distributions compare favorably with certain rocket experiments and laboratory data. From the loss processes, the lifetimes of N and NO are computed. ix

1. INTRODUCTION Distributions of ions and neutral particles with altitude have been obtained by rocket-borne mass spectrometers and are computed from reaction rates of upper atmospheric constituents-ions, electrons, and neutral particles. The reaction rates are obtained from laboratory experiments or from theoretical computations. For obtaining the distribution of minor constituents of the atmosphere like N and NO, mass spectrometers may introduce uncertainties due to "wall effect" or dissociation of molecules by accelerated electrons. Again, to determine rates of reactions experimentally for thermal and nearly thermal ions, difficulties are experienced. In theoretical work too, techniques for calculating cross-sections of reactions involving atmospheric particles are yet to be evolved possibly by semiclassical treatments, and methods for calculating cross sections at thermal energies should be devised. Also in many cases, temperature variations of rate coefficients, which may be altered by a factor of several orders by the ambient temperature range at different layers of the upper atmosphere, are not available. However, the altitude distributions of atmospheric ion and neutral particle densities computed with the available collisional data may cross check those obtained by rocket-borne experiments or from rate coefficients determined in the laboratory. Also from the loss processes, the life times of atmospheric particles can be computed. In this report the altitude distribution of N-atom density between 100 and 280 km is calculated. Since in many cases, reactions involving loss of N atoms are related to the production of NO molecules, its altitude distribution is also calculated. The lifetimes of these particles are also computed. 1

2. COMPUTATION OF N AND NO DISTRIBUTIONS AND LIFETIMES For computing N-atom distribution, the following scheme has been adopted: First, to postulate from geophysical observations and laboratory data, conceivable collisional reactions involving N atoms in the atmosphere. Second, to determine the relative importance of these reactions and for a particular reaction its importance at different layers of the atmosphere, after closely examining the rate coefficients of these reactions as determined by different investigators. A distribution is then obtained by equating the production and loss rates. The reactions leading to the production of N atoms and their observed rate coefficients obtained by different authors are given in Table 1. The coefficients which are used for the computation are given in the last column. The loss processes and their rate coefficients are given in Table 2. The reactions which produce NO molecules and those by which they are consumed are given in Tables 3 and 4. 0, 02, and N2 profiles and the temperature distribution of the atmosphere are obtained from CIRA, 1965. For calculating N-atom distribution, a profile of NO is needed which is initially taken for 100-120 km from the Handbook of Geophysics (1960) and for the altitude range 120-280 km from Nawrocki and Papa (1963). After obtaining the NO distribution from reactions given in Tables 3 and 4, the N-atom distribution is recalculated. The ion distributions (Fig. 1) used for computations are given in Table 5. The electron density is assumed to be the sum of the ion densities. 3

TABLE 1 REACTIONS LEADING TO N-ATOM PRODUCTION AND THEIR RATE COEFFICIENTS Rate Coefficient Used For Campu-tation Observed Rate Coefficient (cm3 particle- sec-l) Reaction (cm3 particle-1 sec-1) Coefficient Coefficient Varying at 300KK With Temperature N++e+N+N 1-2x10-7 (Gibbons, 1961) by mass 3x10-7 * spectrometric technique 3x10-7 (Biondi, 1963) for thermal (3000K) electron 7x10-7 (Nawrocki, et al., 1963) NO++e+N+O 3.5x10-7 (Whitten, et al., 1965) 3.5x10-7 Varies as T-1 from at 300"K 2x10-8 at 20000K to 6x10-7 at 208~K o-0'7 (Sugden, 1961) at flame temperature O++N2+NO++N 3xlO012 (Fehsenfeld, et al., 1965b) 2x10-12 4.2x10-12 exp(-470/RT) 2x10-12 (Danilov, 1966) (E = 0.47 Kcal) 1.4x10-11 (Dickison, et al., 1960) Adjusted to 2x10-12 at 4.7x1012 (Langstroth, et al., 300~K, E is the activa1962) tion energy. 2.2x10~l- (Galli, et al., 1963) 6.75x10-12 (Talrose, et al., 1962) N2+O+NO++N 2. 5x1010 (Ferguson, et al., 1965) 2.5x1010 1. x10-7 exp(-3560/RT) (E = 3.56 Kcal) Adjusted to 2.5x10-10 at 300 K N++02-2++N 5x1010 (Fehsenfeld, et al., 1965) lx109 lx10-9 1xlO-9 (Goldan, et al., 1966) N++NO+NO++N 8xlO-10 (Goldan, et al., 1966) 8x1010 at 3000K O++NO+-++N 2.4xlO-ll (Goldan, et al., 1966) 2.4x10-11 * N2+hvwN2(alcg) Cross-section, Q = 6x10-23 cm2 Q = lx1-21cm2 Q = lxl-2lcm2 (Ditchburn, et al., 1959) ~N+N 10-21 cm2 (Watanabe, et al., 1953) - *After computing the N-atom production rates for rate coefficients at 300~K, it was found that for reactions marked (*), the contributions are small and hence for varying temperature these reactions are not considered. **Most of the absorption occurs in the (8,0) band at 1226A (Nicolet, 1960). For this wavelength, the absorption cross section of 02 is 4x10-19 cm2 (Watanabe, 1958) and N(hv) = 1.5x109 photons/cm2 sec (Gast, et al., 1965). 4

TABLE 2 REACTIONS LEADING TO N-ATOM LOSS AND THEIR RATE COEFFICIENTS Rate Coefficient Used For Computation Observed Rate Coefficient (cm3 particle"l sec-1) Reaction (cm3 particle-1 sec-1) Coefficient Coefficient Varying at 300~K With Temperature O++N-N0++O 2x10-10 at 300"K (Goldan, et 2x1010 2.9x10-9 exp(-1590/RT) al., 1966) (E = 1.59 Kcal) Adjusted to 2x10-10 at 300*K N2++NN2+N+ < 10-11 1x10-l 4x10-9 exp(-3560/RT) (E = 3.56 Kcal) Adjusted to 1x10-11 at 300 ~K N+N+M*N2+M 7.4Ixl33 cm6 particle-2 sec-1 7.4x10-33 cm6 *, 4* (200-4500K) (Herron, et al., particle-2 1958) sec-1 1.7x10-32 at 300~K (Harteck, et al., 1958) N+0+M+NO+M 1.5x10-32 cm6 particle-2 sec-1 5xl1-33 cm6 (at 300~K) (Kaplan, et al., partic le'2 1958) sec1 5x10-33 (Byron, 1959) N+N+N2+hv < 10"14 (Nawrocki, et al., 1963) 1x10-17 1.7x10-16 T-1/2 Adjusted to 1x10-17 at 300K N+O+NO+hv < 10-14 (Nawrocki, et al., 1963) 1x10'17 1.7x1-16 T-1/2 Adjusted to lxiO'17 at 300~K lxlO'17 (Young, et al., 1963) N+02+NO+ 3.3xl10'12 exp(-3100/T) lxl0-16 3.3x10-12 exp(-3100/T) (Kistiakowsky, 1957) 1x10-16 at 300*K (Harteck, et al., 1957) N+NO+N2+O 8x10-11 at 3000K 2.6x10 ll 1.5xlo-12T1 /2 (Kistiakowsky, 1958) 1-3x1013 at 300*K (Harteck, et al., 1957) 1.5x10"12 T1/2 (Nicolet, 1965a) *After computing the N-atom production rates for rate coefficients at 300~K, it was found that for reactions marked (*), the contributions are small and hence for varying temperature these reactions are not considered. **n(M) is assumed to be equal to n(O2)+O.6n(N2) (Young, et al., 1962). 5

TABLE 3 REACTIONS LEADING TO NO PRODUCTION AND THEIR RATE COEFFICIENTS Observed Rate Coefficient Rate Coefficient Used For Computation Reaction - (cm3 particlel sec1) (cm3 particle-1 sec-l) N+O-NO+hv 1x10-17 (Young, et al., 1963) 1.7x10-16 T1/2 Adjusted to lxlO-17 at 300~K N+O+MONO+M 1.5x10-32 cm6 particle-2 sec-l * at 300"K (Kaplan, et al., 1958) 5x10-33 (Byron, 1959) N+02aNO+O 2x10-13 T-1/2 exp(-300/T) (Nicolet, 1965a) 3.3x10-12 exp(-3100/T) 1xlO'16 at 300~K (Harteck, et al., 1957) 3.3x10-12 exp(-3100/T) (Kistiakowsky, et al., 1957) aN O+NO2NO+O2 3.5x10-12 at 3000K (Ford, et al., 1957b) 2NO 5x10-14 N+NO2NN20+O 3xlO 14 at 300~K (Harteck, et al., 1957) N2+02 2x10-14 N_++O2NO++NO x10-13, E = 7 Kcal (Whitten, et al., 1965) * 4xlO'13 by afterglow technique (Fehsenfeld, et al., 1965a) < 10-14 (Harteck, et al., 1961) < 2.1x10-13 (Galli, et al., 1963) O++N2NO++NO 7.5x10ll T1/2 exp(-6000/RT) 7.5x10-ll T1/2 exp(-6000/RT) (Nicolet, 1965b) < 2x103 (Galli, et al., 1963) *N20 and NO2 do not affect appreciably the NO concentration and hence reactions involving these molecules are not considered. **These reactions are not considered as their contributions for 300lK or for varying temperatures are small.

TABLE 4 REACTIONS LEADING TO NO LOSS AND THEIR RATE COEFFICIENiTS Observed Rate Coefficien-t Rate Coefficient Used for Computation Reaction (cm5 particle-i sec)') (cm3 particle sec') N+NO+N2+0 1.5x10'12 T1/2 (Nicolet, 1965a) 1.5x1O0'2 T1/2 8xlo'11 at 3000K (Kistiakowsky, 1958) NO+03-NO2+O2 5x14O4 at 000K (Ford, et al., 1957a) 1.7x10-14 at 3000K (Johnston, et al., 1951) O+NO+M*N02O+M 5.2x1032 cm6 particle'2 sec' * at 3000K (Ford, et al., 195T7b) O+NO-NO2+hv 2.5xlO-17for average quanta of 4.3x1lO16 T-1/2 5500A (Kaufman, 1958) NO+hv(1216A) Cross-section Q = 2xlO-8 cm? +NO++e Q = 2x1018 cm2 (Watanabe, 1959) NO+hv(1900A) Q = 2x10C19 cm2 Q = 2x10'19 cm? +N+O O+NO^NO++O 2.4x10i11 at 3000K 4.6x108 exp(-4500/RT) -++Nt (Goldan, et al., 1966) (E = 4.5 Kcal) Adjusted to 2.4x1iO-'1 at 3000K 02+NOCNO +02 8x1010 at 3000K 1.5x1O0- exp(-4500/RT) (Goldan, et a1., 1966) (E = 4.5 Kcal) ______________________Adjusted to 8x10-10 at 3000K *These reactions are not considered as their contributions for 000K or for varying temperatures are small.

TABLE 5 ALTITUDE DISTRIBUTIONS OF IONS Ion Altitude Range (km) 0+ 100-200 (Whitten, et al., 1964) 200-250 (Johnson, 1966) 260-280* 0+ 100-240 (Whitten, et al., 1964) 240-280** N2 100-220 (Whitten, et al., 1964) 220-280** N+ 130 (Ghosh, et al., 1964) 140-220 (Johnson, 1966) 220-280** NO+ 100-200 (Whitten, et al., 1964) 200-240 (Johnson, 1966) 240-280** *For the altitude range 260-280 km, 0+ and electron distributions (Cormier, 1965) are assumed same. **Extrapolated to follow the trend given in Fig. 3 (Ghosh, et al., 1964). 8

Assuming rate coefficients for various reactions at 300K given in column 3 of Tables 1 and 2, the production and loss rates of N for the altitude range 100-280 km are computed and are given in Figs. 2-4.* The corresponding rates for rate coefficients varying with temperature given in the last columns of the above tables, are computed and are illustrated in Figs. 4-6. A comparison of Figs. 2-4 with Figs. 4-6 shows that the production and loss rates of N atoms are significantly altered if the temperature variation of rate coefficients, which may sometimes be altered by several orders in the above altitude range, are considered. *For calculating N-atom production by predissociation using the formula 2n(N2)zQN(hv)z (the factor 2 accounts for the production of two neutral atoms), it has been assumed that above altitude z, photons are absorbed mainly by 02, so that the photon flux of frequency v at an altitude z for overhead sun is given by N(hv)z = N(hv) exp(-T) where T(Z) = F aO2n(02)zexp(z'/H2,)dz' z N(hv) = number of photons of frequency v outside the earth's atmosphere = 1.5x109 photons/cm2 sec for 1226A (Gast, et al., 1965) H0o = scale height of 02 molecules at an altitude z Q = cross-section for absorption of 1226A by N2 molecules = 1x1021 cm2 a0 = cross-section for absorption of 1226A by 02 molecules = 4x10-19 cm2 (Watanabe, 1958) n(N2)z = concentration of N2 molecules at altitude z n(02)z = concentration of 02 molecules at altitude z. Again, for calculating the production and loss rates from neutralneutral or ion-neutral particle reactions, the usual formula, namely, the rate is equal to the product of rate coefficient and concentrations of the reacting particles, is used. 9

The calculated rates of production and loss of NO molecules for rate coefficients varying with temperature are shown in Figs. 7 and 8. After calculating the loss rates of N atoms, it is found that the lifetime of N atoms for the altitude range 100-280 km varies between 5.7x10 and 1.^x103 sec (Table 6 and Figs. 4 and 6). The N-atom distribution is calculated by equating the production and loss rates (Fig. 9). In a similar manner for 100-280 km the distribution of NO (Fig. 9), for which the lifetime varies between 3.6x102 and 58 sec (Table 6 and Fig. 8), is calculated. TABLE 6 LIFETIMES OF N AND NO Altitude Lifetime of NO Lifetime of N (km) i(sec) (sec) 100 3.6x102 5.7x104 110 2.9x102 1.9x104 120 2.5x102 5.7x103 130 1.8x102 2. lx10 140 1.2x102 1.3x103 150 9.lxlO1 1.6x103 160 7.4x101 2.2x103 170 6.7x101 2.7x103 180 6.3x101 3.3x103 190 5.9x101 4. x103 200 5.8x101 4.8x1o3 220 7.3x101 7.1x103 240 1.0x102 1 Ox104 250 1.1x102 1.7x104 260 1.2x102 2.2x104 280 1.0x102 3.9x104 10

3. CONCLUSIONS 1. After analyzing various reactions leading to the production and loss of N and NO, it may be concluded that the predissociation of N2 molecules does not contribute significantly to the production of N atoms. In the higher region, they are produced mainly by the ion-atom interchange reaction 0+ + N2 + NO+ + N and in the lower region, jointly with the reaction NO+ + e + N +. N atoms are lost by the following reactions 0+ + N + NO+ + 0 and N + NO + N2 +. The computed N distribution shows that the first reaction is important at the upper and the latter at the lower region. The accuracy of calculated N and NO distributions is limited mainly by the values of rate coefficients of reactions (the coefficients are now believed to be accurate by orders but not by factors) and their temperature variations. For the major portion of 100-280 km altitude range, the NO production and loss rates are given, respectively, by 0+ + N2 + KNO+ + NO and 02 + NO + K2NO + 2. At equilibrium 11

kln(O+)n(N2) = k2n(0O)n(N0) n(NO) = L n(N2) k2 Therefore n(NO) distribution follows (N2) profile and is independent of N-atom distribution (see Fig. 9)2, From the rocket-borne mass spectrometric measurements of neutral constituents in the altitude range 100-200 km, Hedin and Nier (1965) concluded that the concentration of N atoms is about 1% of N2. Again the mass spectrometric data obtained by Schaefer constantly show a small increase of N over laboratory calibrations. Also, from the analysis of peak heights for N and N2 between 100 and 200 km, it is found that atomic nitrogen does not occur more than 3% of N2 (Mirtov, 1964). The computed N distribution shows that at the upper region of the above altitude range N is about 1-3 of N2. in the lower region the percentage is much smaller. Therefore, for accurate determination of N-atom concentration by a rocket-borne mass spectrometer, it should be measured above 200 km where its concentration becomes relatively larger, 3. By observing absorption of solar radiations in a rocket-borne spectrograph with pointing control, Jursa, et al. (1959), obtained the upper limit of NO molecules as 1015 molecules cm-2 above the altitude range 63-87 km Again, Barth (1964) obtained a NO column density of 1.5x1013 molecules cm2 above 125 km. This agrees with the value obtained from the computed curve which gives about 3x1013 molecules cm-2 column1 above this altitude~ 2 4 4. NI(5200A, D- S) line is observed in twilight and night airglows and appears with an intensity less than 5R at night and lOR at twilight (Silver,man, et alL, 1965). Assuming that this line is emitted at 90-100 km and that the lifetime of the N(2D) atom is about 26 hours (Hunten, et al., 1966),,;e concentration of N atoms at twilight can be obtained from the rate of production and quenching of the N(2D) atoms, namely n(N)Bn(hv) = n(N2D)[A+n(M)2'] where n(N) = concentration of normal N atoms n(M) = concentration of third body = n(02)+0.6n(N2) 2 n(ND) = concentration of N( D) atoms A,B = A and B coefficients for 2D-4S transition of N atoms n(hv) = solar photon flux density for 5200A X = rate coefficient for collisional deactivation of N( D) atoms Therefore, the emission rate of 5200A line is given by 12

r = n(N2D)A = (N)Bn(hn) A A + n(M)y Substituting B in terms of A and n(hv) from Planck's formula,* we obtain n(N) r(A+n(M) exp(hv/kT) A D where D = dilution factor = 5.41x10-6, and k = Boltzmann constant. No precise information regarding the quenching cross-section involving metastable atoms is available. According to Laidler (1954) the coefficient of quenching reactions involving nonmetastable atoms is of the order of 10-12 cm3/particle sec. The coefficient for the metastable N(2D) atoms by N2 and 02 is assumed to be one order smaller than the above value, that is, y = 10-13 cm3/particle sec. Assuming the sun's temperature T = 6000~K and the mean altitude of emission of 5200A line at twilight to be 90 km, we obtain n(N) = 3x107 cm-3. The computed N-atom distribution shows that at 100 km the concentration is 1x108 cm-3o *In the visible region the number of photons calculated from Planck's blackbody formula for T = 6000~K agrees with the observed value.

REFERENCES Barth, C. A., J. Geophys. Res. 69, 3301 (1964); Space Research 5, 767 (1965), North-Holland Publishing Company, Amsterdam. Biondi, M. A., Advances in Electronics and Electron Physics, Academic Press, 18, 152 (1963). Byron, S. R., J. Chem. Phys. 0, 1380 (1959). Cormier, R. J., J. C. Ulwick, J. A. Klobuchar, W. Pfister, and T. J. Keneshea, Handbook of Geophysics and Space Environments, 1965, p. 12-8. Danilov, A. D., Cospar Seventh International Space Science Symposium, Vienna, May, 1966, Abstract of Papers. Dickison, P.H.G. and J. Sayers, Proc. Phys. Soc. London, 76, 137 (1960). Ditchburn, R. W., J.E.S. Bradley, C. G. Cannon, and G. Munday, Rocket Exploration of the Upper Atmosphere, Ed. R.L.F. Boyd and J. J. Seaton, Pergamon Press, p. 313, 1954. Fehsenfeld, F. C., A. L. Schmeltekopf, and E. E. Ferguson, Planet. Space Sci. 13, 219 (1965a). Fehsenfeld, F. C., A. L. Schmeltekopf, and E. E. Ferguson, Planet. Space Sci. 13, 919 (1965b). Ferguson, E. E., F. C. Fehsenfeld, P. D. Goldan, A. L. Schmeltekopf, and H. I. Schiff, Planet. Space Sci. 13, 823 (1965). Ford, H. W., G. J. Doyle, and N. Endow, J. Chem. Phys. 26, 1337 (1957a). Ford, H. W. and N. Endow, J. Chem. Phys. 27, 1156 (1957b). Galli, A., A. Giardini-Guidoni, and G. G. Volpi, J. Chem. Phys. 39, 518 (1963). Gast, P. R., A. S. Jursa, J. Castelli, S. Basu, and J. Aarons, Handbook of Geophysics and Space Environments, 1965, p. 16-14. Ghosh, S. N., K. D. Sharma, and A. Sharma, Ind. J. Phys. 38, 106 (1964). Gibbons, J. J., Abstracts of D.A.S.A. Reaction Rate Conference, 1961, Boulder, Colorado, Nat. Bur. Std. (U.S.). 15

REFERENCES (Continued) Goldan, P. D., A. L. Schmeltekopf, F. C. Feshenfeld, H. I. Schiff, and E. E. Ferguson, J. Chem. Phys. 44, 4095 (1966). Handbook of Geophysics, Air Force Cambridge Research Laboratories, Ed. S. L. Valley, 1960. Harteck, P. and S. Dondes, J. Chem. Phys. 27, 546 (1957). Harteck, P., R. R. Reeves, and G. Manella, J. Chem. Phys. 29, 608 (1958). Harteck, P. and R. R. Reeves, Chemical Reactions in the Lower and Upper Atmosphere, Interscience, 1961, p. 233. Harteck, P. and R. R. Reeves, Chemical Reactions in the Lower and Upper Atmosphere, Interscience, 1961, pp. 231, 234. Hedin, A. E, and A. 0. Nier, J. Geophys. Res. 70, 1273 (1965). Herron, J. T., J. L. Franklin, P. Bradt, and V. H. Dibeler, J. Chem. Phys. 30, 879 (1959); 29, 230 (1958). Hunten, D. M. and M. B. McElroy, Rev. Geophys. 4, 303 (1966). Johnson, C. W., J. Geophys. Res. 71, 330 (1966). Johnston, H. S. and H. J. Crosby, J. Chem. Phys. 19, 799 (1951). Jursa, A. S., Y. Tanaka, and F. LeBlanc, Planet. Space Sci. 1, 161 (1959). Kaplan, J. and C. A. Barth, Proc. Nat. Acad. Sci. 44, 105 (1958). Kaufman, F., Proc. Roy. Soc. A. 247, 123 (1958). Kistiakowsky, Go B. and G. G. Volpi, J. Chem. Phys. 27, 1141 (1957). Kistiakowsky, G. B. and G. G. Volpi, J. Chem. Phys. 28, 665 (1958). Laidler, K. J., Chemical Kinetics of Excited States, Oxford University Press, 1954, P. 159. Mirtov, B. A., Gaseous Composition of the Atmosphere and Its Analysis, NASA (1964), p. 133. Mitra, A. P., Advances in Upper Atmosphere Research, MacMillan Company, 1963, p. 57. 16

REFERENCES (Concluded) Nawrocki, P. J. and R. Papa, Atompsheric Processes, Prentice-Hall, Inc., 1963, PP. 3-27. Nawrocki, Po J. and R. Papa, Atmospheric Processes, Prentice-Hall, Inc., 1963, pp. 3-46 (Coeff. is assumed to be same for similar reactions). Nicolet, M., Physics and Medicine of the Atmosphere and Space, Ed. Benson, 0. 0. Jr., and H. Strughold, John Wiley, 1960. Nicolet, M., J. Geophys. Res. 70, 679 (1965a). Nicolet, M., J. Geophys. Res. 70, 691 (1965b)o Schaefer, E. J., Private Communication. Silverman, S. M., G. J. Hermandez, A. L. Carrigan, and T. P. Markham, Handbook of Geophysics and Space Environments, 1965, p. 13-3. Sugden, T. M., Chemical Reactions in the Lower and Upper Atmosphere, Interscience, 1961, p 330. Talrose, V. L., M. I. Markin, and I. K. Larin, Disc. Faraday Soc. 33, 257 (1962). Watanabe, K., M. Zelikoff, and E.C.Y. Inn, Geophysical Research Paper No. 21, June 1953. Watanabe, K., J. Chem. Phys. 22, 1564 (1954). Watanabe, K., Advances in Geophysics 5, 153 (1958), Academic Press. Whitten, R. C. and I. G. Poppoff, J. Atmos. Sci. 21, 117 (1964). Whitten, R. C. and I. G. Poppoff, Physics of the Lower Ionosphere, PrenticeHall, 1965. See Fig. 4., 1, p. 77. Whitten, R. C. and I. G. Poppoff, Physics of the Lower Ionosphere, PrenticeHall, 1965, p. 103. Whitten, R. C. and I. G. Poppoff, Physics of the Lower Ionosphere, PrenticeHall, 1965, p. 122. Young, C. and E. S. Epstein, J. Atmos. Sci. 19, 435 (1962). Young, R. A. and R. L. Sharpless, J. Chem. Phys. 39, 1071 (1963). Young, R. A., J. Chem. Phys. 34, 1295 (1961). 17

300 Ion Distribution + " N+ + (0+ 100%%%N %%_ /If 250O.4 150J)K' 0 20 1500 l l l I 10 010 2 I106 105 10" 10 CONCENTRATION (PARTICLE CM) Fig. 1. Variations of assumed ion densities with altitude. Solid curves are obtained from rocket-borne experiments. The broken curves are extrapolated (see Table 5).

N 300- Constant Rate Coefficient (I) - o++No -O' +N (I) ^.. -rO~+NO-*2+N o (3) (8) (1) (5) (6) (4) (7) (9) (2) — *N2+hv -- N -— *N+N (X:1226A) (3) _ N++NO -- NO++N \ x \ Nf (2) (4) --— NO++e N+ (5) — N -t+e~ —N+N 250 \(6) - N++ O- N + \ -O\ \+N - \(7)~ 0++N2-* NO++N (8).-N+O- NO++N / L - - Total 200 - I \10 I 150 / x / 100 ~103 I0 10' 10' 1 103 104 10" PRODUCTION RATE (PARTICLE CM3 SEC1 ) Fig. 2. Production rates of N atoms by various reactions for rate coefficients at laboratory temperature (300~K) assumed constant for the whole altitude range.

N 300- Constant Rate Coefficient -_~~~~ ~~( 1)...N +OM -NO+M (2) (4) (3) (5) (6) (7) (2)__N2N N2+N \ ^~~~~~~\ ~~\ \ \,~~~3\ ~ N +O - NO + hv (4) N+O2 NO+O NF \^^~~ \x \ \ \\~(5) - 02+N NO++O 250 \ () N NOi) -N2+O N- \\ Total 01-L 200 150 100 10~ 10" 108 10 o" 1o" 10 x(SEC') Fig. 3. Variation of x with altitude for rate coefficients at laboratory temperature (300~K) assumed constant for the whole altitude range. To obtain loss rate of N atoms, multiply x by [NJ.

300 N ( N +N - N2+ hv (assuming const. rate coeff.) (2) — x N+N- N2+ hv (assuming rate coeff. varying with temp.) 2 (3) N +N + M -N2+M (assuming const. rate coeff.) 250'x,'^~~~~~~~~~~~~~~~~~~~~~~~~~x I 200LJ 5: x\ 150- (3) \ 100- -22 10o- 102 0 10 10-8 10-7 x'(CM3 PARTICLE' SEC ) Fig. 4. Variation of x' with altitude for reactions involving 2 nitrogen atoms. To obtain loss rate multiply x' by [N]2. Loss rates by three-body reactions are very small compared with those for two-body reactions.

300 N Rate Coefficient Varying With Temp. (j).... NO++e > N+O (- 2)~ (l) (21) _ —-- - - -- N' N+O-NO++N \ (3) -x- O+ 0 N2- NO++N |\ \ (4) — c N++O~2 3- O +N o(5) _ \ Total 250N 200 2 H__/ / I \ \ 10' t02 103 o04 i05 PRODUCTION RATE (PARTICLE CM-3 SEC-I) Fig. 5. Production rates of N-atoms by various reactions for rate coefficients varying with temperature. 22

N 300[- Rate Coefficient Varying With Temp. (I)....N +0~ — NO +hv \(1) \? (7)') (4)5) ( 6) (2) — N2'+N N2+Nf - \ \ (3)-. — N2+02 -NO+O \ \ \\ \\ \ (4)~~- 02++ N -NO++O 250N- \ (5)- N + NO(l) —N2+0 | \ \\\ > (6) Total of (I),(2)(3)(4b),nd(5) ~E ~ \ \ \\ N (7L —., N+NO(4)- N2+0 0\ \ \\ (8)-.- Total of (I),(2)(3),(4),and(7) Ir \ LUJ 100- / 150 - / 10-9 10 17 10 10o5 10 100x (SEC') Fig. 6. Variation of x with altitude for two-body reactions having rate coefficients varying with temperature. Loss rate = x [N]. NO(1) and NO(4) represent NO density obtained from Curves (1) and (4) of Fig. 9, respectively.

NO 300 - Rate Coeff. Varying With Temp. (1) mO+N2 NO+NO (2) o -N+02 -NO+O - / (3) 1(2) (1)'(4) (3) - N+O — NO+ h \ 1'(4)1 Total 250 LU 200 N 150 100l' 1~ I~ 10' 102 103 10 10 0 PRODUCTION RATE (PARTICLE CM3 SEC" ) Fig. 7. Production rates of NO molecules by various reactions with rate coefficients varying with temperature.

NO 300- Rate Coeff. Varying With Temp. (I) 0 --- +NO - N02+ h/ (4) \(2) (3) (5) (2) -x- O2+NO — NO++O / V (3)~ - O++NO —-NO++O 250 2 (4) - N+NO -N2+0 (5) Total - 200 Ir^~~ X I I 100 I2 l0o6 10-5 104 10-3 102 x (SEC-') Fig. 8. Variation of x with altitude for various reactions having rate coefficients varying with temperature. To obtain loss rate of NO molecules, multiply x by [NO]. 25

300250o- \ / E 200 150 loo00.3)/"'2) 50l b o N o 105 10607 108 K)9 1010 CONCENTRATION (PARTICLE CM3) Fig. 9. Computed altitude distributions of N and NO. For comparison, the distributions of 0, 02 and N2 obtained from CIRA 1965 are also shown. (1) Assumed NO distribution; (2) N distribution for (1) for constant rate coefficient; (3) N distribution for (1) for rate coefficient varying with temp.; (4) calculated NO distribution for (3) for rate coefficient varying with temp.; (5) N distribution calculated from (4); (6) N2 distribution from CIRA 1965; (7) 0 distribution from CIRA 1965; (8) 02 distribution from CIRA 1965. 26