Kinetics of theF + NO2 + M → FNO2 + M reaction studied by pulse radiolysis combined with time-resolved IR and UV spectroscopy

5 April 1996

CHEMICAL PHYSICS LETTERS ELSEVIER

Chemical Physics Letters 252 (1996) 165-171

Kinetics of the F + NO 2 + M --->FNO 2 + M reaction studied by pulse radiolysis combined with time-resolved IR and U V spectroscopy Palle Pagsberg a, Alfred Sillesen a, Jerzy T. Jodkowski b, Emil Ratajczak a,b a Environmental Science and Technology Department, Rise National Laboratory, DK-4000 Roskilde, Denmark b Department o f Physical Chemistry, Wroclaw University of Medicine, Pl. Nankiera 1, 50-140 Wroclaw, Poland

Received 13 November 1995; in final form 1 February 1996

Abstract The title reaction was initiated by the pulse radiolysis of SF6/NO 2 gas mixtures, and the formation of FNO 2 was studied by time-resolved infrared spectroscopy employing strong rotational transitions within the v~ and v4 bands of FNO 2. The pressure dependence of the formation kinetics was studied with SF6 pressures of 5-1000 mbar at 298 K. Comparative studies were carried out by monitoring the decay kinetics of NO 2 at 445 nm using pressures of 100-1000 mbar at 295 and 341 K. The observed pressure dependence is represented in terms of a fall-off curve with the following values of the limiting high- and low-pressure rate coefficients, krec.~ = (2.1 +__1.0) × 10 l° (T/300) °'Is M - l s- 1 and kre¢,0/[SF6] = (3.8 _ 1.8) × 1012 (T/300) -2"4 M -2 s - l in the temperature range 200-400 K, and with a broadening factor, Fcent=0.587× (T/300) -°.32.

I. Introduction The title reaction has previously been studied by mass spectrometry of F atoms produced by microwave discharge of H e / F 2 mixtures in a flow reactor [1]. The observed pressure dependence was explained in terms of the termolecular reaction F + NO 2 + M --->FNO 2 + M with a rate constant of 2.3 × 10 ~ M -2 s -~ at 300 K. The possible formation of the isomeric species FONO has been discussed in a more recent investigation where the reaction was studied by observing the time profiles of infrared flourescence from vibrationally excited H F molecules produced in the competing reaction F + H 2 ~ HF *

+ H [2]. The observed pressure dependence ascribed to the overall reaction, F + NO 2 + M ~ products was analysed to obtain limiting rate constants of k 0 / [ N 2 ] = ( 3 . 6 + 0 . 6 ) × 1011 M -2 s - l and k ~ = ( 1 . 9 + 0 . 5 ) X 101° M - l s - l A limiting high-pressure value of 1.21 × 10 lj M-~ s-~ has been recommended in the most recent data evaluation [3]. In the present investigation we have employed time-resolved infrared absorption spectroscopy to study the formation of FNO 2, and for comparison the decay of NO 2 was studied by ultraviolet spectroscopy. We find no experimental evidence for the formation of the isomeric species FONO.

0009-2614/96/$12.00 © 1996 Elsevier Science B.V. All rights reserved PH S0009-2614(96)00161-3

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P. Pagsberg et a l . / Chemical Physics Letters 252 (1996) 165-171

2. Experimental The experimental apparatus for pulse radiolysis combined with time-resolved infrared diode laser spectroscopy has been described previously [4]. Briefly, F atoms were produced by pulse radiolysis of SF6 which was used as the bath gas with pressures in the range of 5-1000 mbar. The yields of F atoms obtained with varying total pressures of SF6 were determined by monitoring the decrease in the infrared absorption of C H 4 consumed in the titration reaction, F + CH 4 --~ HF + C H 3. Using a strong rotational transition of C H 4 at 1332.721 cm - t we have determined the absorption cross section at the line center and the effect of pressure broadening by the addition of SF6. The lineshape was scanned before and after electron pulse irradiation to determine the amount of C H 4 consumed in the titration reaction carried out under experimental conditions where [F] 0 = A[CH 4] << [CH4] 0. Based on the yield of F atoms we have been able to determine absolute infrared absorption cross sections of FNO 2 produced by radiolysis of SF6/NO 2 mixtures. High-resolution infrared spectra of FNO 2 were recorded with an optical path length of 400 cm obtained by adjustment of internal mirrors in the white cell using a H e - N e laser for alignment. Previously only low-resolution infrared spectra of F N O 2 have been reported [5,6]. Strong bands centered at 1309.6 and 1791.5 c m -1 have been assigned to v I (sym. NO 2 stretch) and v4 (asym. N O 2 stretch), respectively [5]. In the present investigation we have observed a large number of strong rotational lines within the v I and v4 bands in regions free of interference from the spectra of SF6 and N O 2. The lineshape was studied as a function of the bath gas pressure. Significant pressure broadening was observed with p(SF 6) > 20 mbar, and with p(SF 6) = 1000 mbar the rotational fine structure disappeared due to overlap between the pressure broadened rotational lines. However, it was still possible to study the formation kinetics of the product even with a bath gas pressure of 1000 mbar. The effect of pressure broadening was counterbalanced by the increase in the stopping power for high-energy electrons and the primary yield of F atoms. The experimental results obtained by infrared spectroscopy were compared with NO 2 decay kinetics studied by pulse radiolysis combined with time-resolved ultraviolet

spectroscopy. The experimental apparatus has been described in detail in a previous publication [7]. Time profiles of the N O 2 consumption were monitored at 445 nm under typical pseudo-first-order conditions to determine the overall rate constant for the reaction as well as the initial yield of F atoms produced by radiolysis of SF6/NO 2 mixtures, [F] 0 = A[NO 2 ].

3. Results and discussion

3.1 Experimental studies Reaction (1) was initiated by pulse radiolysis of SF6/NO 2 mixtures at 298 K. In the absence of NO 2 the decay of F atoms takes place via the pressure dependent combination reaction (2) which must also be taken into account in the presence of small amounts of NO 2 where the F atoms are consumed in both of the competing reactions, F +NO 2 +M ~FNO 2 +M,

(1)

F + F + M - - * F 2 + M,

(2)

Thus, the initial decay rate of F atoms is described by the expression - (d l n [ F ] / d t ) t = o = k* = k2[M][F]o + k,[M][NO2 ] o. The last term becomes dominating at high NO 2 concentrations, i.e. under pseudo-first-order conditions where the decay of F atoms and the formation of FNO 2 can be expressed by a single exponential function, [F] = [F] 0 e x p ( - k" t) and [FNO z ] = [F] 0 ×[1 -- e x p ( - k* t)]. The kinetics of reaction (1) was studied by monitoring the time profile of the infrared absorption due to FNO 2. A large number of rotational lines have been observed in the range of 1320-1350 cm - l within the R branch of the v~ band of FNO 2. Fig. 1 shows a typical example of the rotational fine structure observed with a total pressure of p(SF6) = 10 mbar. For kinetic studies we have selected a strong line at 1342.31 cm-1 for which we have determined an apparent absorption cross section of (2.26 + 0.10) × 10-18 cm 2 molecule-1 with a bath gas pressure of 100 mbar. Due to pressure broadening the absorp-

P. Pagsberg et al./ Chemical Physics Letters 252 (1996) 165-171

0.2

i

167

10

i -1

vl(FN02)

=

R-branch

1309.6

om

transitions

a 0.0

o

,

t

o

7w a

o4 o

1321.2

1321.4 Is C n l

1321.6

-1

Fig. 1. Rotational fine structure of FNO 2 observed after pulse radiolysis of a gas mixture containing 0.2 mbar NO 2 in 10 mbar

2

S F 6.

tion cross section at the line center is strongly dependent of the bath gas pressure, and we have estimated a limiting low pressure value of 2.7 × 10 -17 c m 2 molecule - t , i.e. the Doppler limit at 298 K. Thanks to the high absorption cross section it has been possible to monitor the formation kinetics of FNO 2 with a good signal-to-noise ratio at varying pressures. The insert in Fig. 2 shows an example of the formation kinetics observed by pulse radiolysis of a gas mixture containing 0.60 mbar NO 2 and 99.4

0

0.0

t

1

0.5

1.0

1.5

p(N0e) / mbar Fig. 2. FNO 2 formation kinetics observed at 1342.3 and 1784.0 c m - i. The reaction was initiated by pulse radiolysis of NO 2 / S F 6 mixtures using a total pressure of p(NO 2 + S F 6 ) = I00 mbar at 298 K.

mbar SF6 at 298 K. The experimental absorption versus time curve was analyzed by least-squares fitting of the expression A = Amax[1 - e x p ( - k* t)]

Table 1 Experimental conditions and results on the pressure dependent addition reaction F + NO 2 + M --* FNO 2 + M at 298 K with M = SF6 Bath gas p(SF6) (rabar)

10S[F]0 (mol/l)

105[NO2 ]o (mol/I)

10- 3k * (s- i)

Number of experiments

10- 9 krec ( M - ] s - 1)

Notes

5 10 18 32 56 100 180 320 560 10(30

2.3 4.7 8.5 15 26 47 85 150 260 470

0.20-1.12 0.40-2.20 0.40-3.20 0.40-4.40 0.40-4.44 0.80-5.68 1.60-6.00 2.20-11.5 2.00-7.20 4.00-13.6

1.04-2.17 1.56-5.47 2.89-13.4 4.24-25.4 8.00-40.1 17.3-71.5 40.1-104 83.5-260 74.3-208 248 -546

12 15 11 14 12 22 11 10 9 8

0.120 0.219 0.379 0.529 0.783 1.10 1.46 1.90 2.45 3.07

a, a, a, a, a, a, a, a, a, a,

a b c d

FNO2 formation kinetics monitored at 1342.3 cm - ] . Estimated uncertainties of k~c are in the range 5-10%. FNO2 formation kinetics monitored at 1784.0 c m - 1. Estimated uncertainties of kre c a r e in the range 10-20%.

b b, c b b b b, c d d d d

168

P. Pagsberg et a l . / Chemical Physics Letters 252 (1996) 165-171

to obtain best-fit values of A m a x = 0 . 1 1 0 + 0 . 0 0 5 and k* = (3.5 _ 0.1) × 10 4 s - I. The formation kinetics were studied at varying partial pressures in the range p ( N O 2) - - 0 . 2 - 1 . 4 mbar backed up with SF6 to a total pressure o f 100 mbar. Similar experiments were carried out using rotational transitions within the v4 band of F N O 2. The kinetic results obtained with different vl and v 4 band transitions were found to be identical within the experimental uncertainties. The linear plot of k* versus p ( N O 2) shown in Fig. 2 is well accounted for by reaction (1) proceeding under pseudo-first-order conditions. The non-zero intercept at p ( N O 2) = 0 is due to the competing reaction (2) which becomes increasingly important at low NO 2 concentrations. The apparent bimolecular rate constant obtained with a constant bath gas pressure of p ( S F 6) = 100 mbar was found to be k I = 1.10 × l09 M - l s - l with an estimated uncertainty of + 15%. Similar kinetic studies were carried out with different bath gas pressures in the range p ( S F 6) = 5 - 1 0 0 0 mbar, and the results are summarized in Table 1. The strong pressure dependence observed in the lower part o f the fall-off curve is accounted for in terms of the low-pressure limiting third-order reaction F + NO 2 + M ~ F N O 2 + M. At higher pressures the rate constant approaches the limiting high-pressure value, which has been evaluated in the theoretical section. The experimental results presented above are based on studies of F N O 2 formation kinetics. Supplementary studies were carried out

by monitoring the decay rate of NO 2 at varying bath gas pressures and temperatures. The reaction was initiated by pulse radiolysis of SF6//NO 2 mixtures, and time profiles of NO 2 consumption were monitored at 445 nm. The insert in Fig. 3 shows an example of NO 2 kinetics observed on a timescale of 100 ~s. The initial yield of F atoms was derived from the observed decrease in the absorption of NO2, i.e. [F] 0 = A A(445 n m ) / o ' L using an updated value o f t r ( N O 2) -- 6.12 × 10-19 cm 2 m o l e c u l e - l at 445 nm [8]. Again, all experiments were carried out under pseudo-first-order conditions, using concentrations o f [NO2] 0 : ~ [F] 0. The curve shown in the insert was analysed by a simple curve-fitting procedure to derive a pseudo-first-order rate constant of k* = 1.42 × 105 s - 1 observed with p ( N O 2) = 0.5 mbar. Fig. 3 shows a summary of the experimental results obtained with constant bath gas pressure o f p ( S F 6) = 560 mbar at 341 K. A himolecular rate constant of 2.82 × 109 M - 1 s - l was derived from the slope of k* versus p(NO2). Similar experimental studies were carried out with varying bath gas pressures, and at two different temperatures. The results are summarized in Table 2. A comparison between the results presented in Tables 1 and 2 shows that the rate constants derived from NO 2 decay kinetics are systematically higher than those obtained by infrared studies o f F N O 2 formation kinetics. At a total pressure of 100 mbar the rate constants are the same within the experimental un-

Table 2 Experimental conditions and results on the pressure dependent addition reaction F + NO2 + M ~ FNO2 + M with M = SF6 (kinetics of NO2 decay monitored at 445 nm)

T (K) 295 295 295 295 295 295 341 341 341

p(SF6)

106[F]o

105[NO2]o

10- 4k *

Number of

10-9krec

(mbar)

(mol/l)

(mol/l)

( s - i)

experiments

( M - I s - l)

100 180 320 560 1000 1000 320 560 1000

0.6 1.0 1.9 3.2 3.2 5.8 1.9 3.2 3.2

1.60-6.00 1.20-6.40 1.20-6.00 1.80-6.80 1.20-6.40 2.00-6.00 1.97-5.37 1.61-5.73 1.79-6.09

2.38-7.08 3.18-9.38 8.27-19.3 12.6-29.5 9.56-30.8 17.4-31.2 5.60-12.4 6.82-17.9 10.7-27.6

13 14 15 7 7 8 7 I1 11

1.02 1.78 2.28 3.50 4.08 3.90 1.91 2.82 3.44

a Maximum irradiation dose. b Estimated uncertainties of k are in the range 10-20%.

c Reduced irradiation dose (56%). d Estimated uncertainties of k are in the range 15-25%.

Notes a, b a, b a, b a, b b, c a, d a, d a, d c, d

P. Pagsberg et al. / Chemical Physics Letters 252 (1996) 165-171 8.0

2.6

169

cluded in the following theoretical analysis of the pressure dependent combination reaction.

tooo

j

3.2 Theoretical analysis o f the f a l l - o f f curve F o l l o w i n g the concepts of Troe and co-workers [9,10] the rate constant kre¢ for a pressure d e p e n d e n t r e c o m b i n a t i o n reaction in the fall-off range can be expressed by

8.0

7 1.11

=

krec,0/krec,®

1 + ko,r¢c/k,~¢,=

F,

(3)

where k~e¢,= and krec,0 represent the limiting highand l o w - p m s s u m rate constants, and F is the " b r o a d e n i n g factor" which can be expressed b y

1.0

0.0 0.0

log Fcent

log F =

0.5

(4)

1 + [log(krec,0/krec,®)/N] 2"

0.5

1.0

1.5

8.0

p(N08) / m b a r Fig. 3. NO2 decay kinetics observed at 445 nm. The reaction was initiated by pulse radiolysis of NO2/SF 6 mixtures using a bath gas pressure of p(SF6) = 560 mbar at 441 K.

certainties. A t higher bath gas pressures the difference increases steadily towards a m a x i m u m o f about 25%. The m a s o n for this discrepancy is m o s t likely a systematic error associated with the m e a s u r e m e n t s of the low partial pressures o f N O 2 e m p l o y e d in the experimental studies o f N O 2 decay kinetics. H o w ever, all of the experimental results have b e e n in-

The b r o a d e n i n g factor Fce.t and the value of N = 0 . 7 5 - log Fce.t were derived as described in detail in Refs. [9,10] The high-pressure l i m i t i n g rate constants, k~ec® was calculated u s i n g a v e r s i o n o f the statistical adiabatic channel m o d e l ( S A C M ) , the m a x i m u m free energy m e t h o d o f Q u a c k a n d Troe [11] and the factorized version d e v e l o p e d b y Troe [12]. Both methods are semi-empirical and kr~~ depends o n the values of two parameters, i.e. the Morse parameter, fl and an interpolated " l o o s e n e s s " parameter, a . For a fixed ratio o f c t / f l results obtained by those methods should be n e a r l y equivalent. The low-pressure limiting rate coefficient, kr~c,0 was derived from the expression k ~ , 0 - - / 3 c ~(SC)rec,0 , where k(SC)r~e, 0 is the strong collision low-pressure

Table 3 Thermodynamic functions for the reaction F + NO2 ~ FNO2 (standard state pressure, Po = 0.1 MPa)

T

,xc °,

as °

an?

(K)

(J mol- l K- 1)

(J mol- t K- 1)

(kJ tool- t)

0 100 200 298.15 300 400 500 1000

-

0.000 20.869 16.997 11.074 10.973 - 6.551 - 3.683 1.592

-

0.000 120.393 134.015 139.737 139.737 142.245 143.376 143.820

-

215.407 217.488 219.431 220.802 220.822 221.683 222.185 222.357

log rp + 107.314 50.309 31.388 31.149 21.518 15.722 4.102

P. P ag sberg et al. / Chemical Physics Letters 252 (1996) 165-171

170

l

limiting rate coefficient evaluated in terms of the factorized expression [13,14]. The collision frequency, tic is related to the average energy transferred per collision ( E ) and the factor F e representing the energy dependence of the density of states,

~c

T = 298 K o • SF 6 ix N 2

10

• He [] A r

- -

FEkr

"7

Molecular parameters of reactant and product molecules have been reported [6,15,16], and ideal gas thermodynamic functions for the reaction F + NO 2 ~ FNO 2 are presented in Table 3. Based on a value of VRc = 568 cm-1 for the F - N O 2 reaction coordinate and a threshold energy of E 0 = 215.4 kJ m o l - l a value of the Morse parameter o f / 3 = 1.8 .~-1 was derived and used for the determination of krec,~. Lennard-Jones parameters for FNO 2 , o - = 4.0 A and E l k = 260 K were derived using Lydersen's method [17]. All factors used in the calculation of krec,0 were derived as described in Ref. [13]. There are no experimental data available which may be used to estimate the limiting high-pressure rate coefficient, kr~,~. Fasano and Nogar [2] derived a high-pressure value of 1.9 × 101° M -1 s - I based on experiments carried out in a limited pressure range of 13-175 mbar of N:. For many addition reactions a realistic estimation of the high-pressure value, kr~c,~ can be obtained theoretically using the SACM method with the ratio of a / / 3 = 0.46 + 0.09 [18]. Using the maximum free energy method with values of a = 0.83 ~k-] and /3 = 1.8 ,~-1 we obtained a value of k~c,® = 2.1 × 101° M -1 s -1 at 298 K. This value is close to the value of 1.9 × 10 l° M - i s - l reported by Fasano and Nogar [2]. The best theoretical fit using the fall-off Eq. (3) with kr~c~ = 2.1 × 101° M -1 s -1 at 298 K and M = SF6 was obtained with - ( A E ) S F 6 = 2.8 kJ mo1-1. This corresponds to a value of k ~ , 0 / [ S F 6] = 3.8 × 1011 M -2 s - l with F¢~nt= 0.596, and the center of the

=S

g

T=341

o

10

0

1

K

M = SF 6

2

3

IogpMImbar Fig. 4. Experimental fall-off curve for the reaction F + N O 2 + M F N O 2 + M with M = SF6 in c o m p a r i s o n with the theoretical h i g h - and low-pressure limiting rate constants. E x p e r i m e n t a l data for M = He are taken from Ref. [1] a n d those f o r M = N 2 and A r from Ref. [2]. There is overlap b e t w e e n the fall-off curves for M = S F 6 a n d M = N 2.

fall-off curve at 1370 mbar at room temperature. The theoretical fall-off curves in comparison with experimental results are shown in Fig. 4. Our value of krec.®= 2.1 × 10 l° M -1 s -J obtained at room temperature may be compared with reported rate constants for other addition reactions, C I + N O 2 ~ C 1 N O 2 of 6 . 0 × 1 0 1 ° M - 1 s - ] [19], Br + NO 2 ~ BrNO 2 of 1.6 × 10 l° M - ~ s - l [20] and I + NO 2 --* INO 2 of 4.0 X 101° M - ] s- l [3]. Table 4 summarizes recalculated values of kr~c,0 for previ-

Table 4 Limiting low-pressure rate constants, krec. o a n d b r o a d e n i n g factors, Fcent for different bath gases, M at 298 K Bath gas M

10 - i 1(krec.o)sc/[M] (M - 2 S- 1)

/3c

- (A E ) M (kJ t o o l - l )

10 11krec.o/[M] (M- 2 s- l)

Fcen t

SF6 N2 He

9.54 8.78 10.7

0.397 0.426 0.247

2.8 3.2 1.3

3.8 + 1.8 3.6 + 1.8 2.6 5 : 0 . 8

0.596 0.613 0.575

- -

P. Pagsberg et al. / Chemical Physics Letters 252 (1996) 165-171

ous e x p e r i m e n t a l results with M = He [1] and M = N 2 [2]. T h e h i g h e r value o f ( A E ) N 2 is e x p l a i n e d in terms o f the large discrepancies b e t w e e n the reported e x p e r i m e n t a l results, and in particular at l o w e r pressures o f N 2 which m a y lead to an overestimate o f krec,0/[N2]. In order to investigate the temperature d e p e n d e n c e o f the rate coefficients w e h a v e carried out a series o f e x p e r i m e n t s at 341 K as s h o w n in the insert o f Fig. 4. A theoretical analysis o f these data g a v e the f o l l o w i n g values o f kr~c,~= 2 . 1 4 × 10 l° M -1 s -1 and k r e c , 0 / [ S F 6 ] = 2 . 8 × 1 0 It M - E s -1 based on k(SC)r~c.0/[SF6] = 7.62 × l 0 II M - 2 s -1 and Fcent = 0 . 5 7 2 . A s s u m i n g that the v a l u e s o f ( A E ) S F 6 and a are independent o f temperature in the range o f 2 0 0 - 4 0 0 K the temperature d e p e n d e n c e o f the limiting high- and low-pressure rate coefficients can be e x p r e s s e d as follows: k~c,~ = (2.1 + 1.0) × 1 0 1 ° ( T / 3 0 0 ) °'Is M -1 s -1 and krec,0/[SF6] = (3.8 _ 1 . 8 ) × 1 0 1 1 ( T / 3 0 0 ) -2"4 M - 2 s -1 with Fcent = 0 . 5 9 6 ( T / 3 0 0 ) -°'a2. T h e o b s e r v e d temperature dep e n d e n c e is similar to those reported for other simple radical assocoation reactions.

Acknowledgement The financial support f r o m the Danish Natural Science and R e s e a r c h Counsil to our visiting scientist, Professor E m i l Ratajczak is gratefully a c k n o w l edged.

References [1] C. Zetzsch, in: European Symposium on Combustion, ed. F.S. Weinberg (Academic Press, London, 1973) p. 35.

171

[2] D.M. Fasano and N.S. Nogar, J. Chem. Phys. 78 (1983) 6688. [3] R. Atkinson, D.L. Baulch, R.A. Cox, R.F. Hampson, Jr., J.A. Kerr and J. Troe, J. Phys. Chem. Ref. Data 18 (1989) 881. [4] P. Pagsberg, E. Ratajczak and A. Sillesen, in: Research in chemical kinetics, Vol. 1, eds. R.G. Compton and G. Hancock (Elsevier, Amsterdam, 1993) p. 65. [5] D.L. Bemitt, R.H. Miller and I.C. Hisatsune, Spectrochim. Acta 23A (1967) 237. [6] K.O. Christe, C.J. Schack and R.D. Wilson, Inorg. Chem. 13 (1974) 2811. [7] P. Pagsberg, O.J. Nielsen, and C. Anastasi, in: Advances in spectroscopy, Vol. 24, eds. R.J.H. Clark and R.E. Hester (Wiley, Chichester, 1994) p. 263. [8] W. Schneider, G.K. Moortgat, G.S. Tyndall and J.P. Burrows, J. Photochem. Photobiol. 40 (1987) 195. [9] J. Troe, Ber. Bunsenges. Physik. Chem. 87 (1983) 161. [10] R.G. Gilbert, K. Luther and J. Troe, Ber. Bunsenges. Physik. Chem. 87 (1983) 169. [11] M. Quack and J. Troe, Ber. Bunsenges. Physik. Chem. 81 (1977) 329. [12] J. Troe, J. Chem. Phys. 75 (1981) 169. [13] J. Troe, J. Chem. Phys. 66 (1977) 4758. [14] J. Troe, J. Phys. Chem. 83 (1979) 114. [15] M.W. Chase Jr., C.A. Davies, J.R. Downey Jr., D.J. Fmrip, R.A. McDonald and A.N. Syverud, JANAF Thermochemical Tables, 3rd Ed. J. Phys. Chem. Ref. Data Suppl. 1 14 (1985). [16] V.P. Gluschko, L.V. Gurvich, G.A. Bergman, I.V. Veyts, V.A. Medvedeev, G.A. Chachkuruzov and V.S. Yungman, Termodinamitcheskoe svoistva individualnych vestchestv, Vol. 1, Part 2. (Nauka, Moscow, 1978). [17] R.C. Reid and T.K. Sherwood, The properties of gases and liquids, 2nd Ed. (McGraw-Hill, New York, 1966). [18] C.J. Cobos and J. Troe, J. Chem. Phys. 83 (1985) I010. [19] W.B. DeMore, D.M. Golden, H.F. Hampson, C.J. Howard, M.J. Kurylo, M.J. Molina, A.R. Ravishankara and S.P. Sander, Chemical kinetics and photochemical data for use in stratospheric modeling, JPL Publ. 87-41 (1987) 1. [20] R. Atkinson, D.L. Baulch, R.A. Cox, R.H. Hampson, J.A. Kerr and J. Troc, J. Phys. Chem. Ref. Data 21 (1992) 1125.