DTIC ADA406412: Temperature Dependence of the Cl + HN(3) Reaction from 300 to 480 K

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27 Aug 1999 Journal Article 9/97 - 6/99
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Temperature Dependence of the C1 + HN3 reaction form 300 to
480 K 5b. GRANT NUMBER
5c. PROGRAM ELEMENT NUMBER
6.A UTHOR(S) 5d. PROJECT NUMBER
Gerald C. Manke II, Thomas L. Henshaw, Timothy J. Madden, 3326
Gordon D. Hager 5e. TASK NUMBER
LA
5f. WORK UNIT NUMBER
02
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT
NUMBER
Air Force Research Laboratory
Directed Energy Directorate
3550 Aberdeen Ave. SE
Kirtland AFB, NM 87117
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)
Air Force Research Laboratory
Directed Energy Directorate
3550 Aberdeen Ave. SE 11. SPONSOR/MONITOR'S REPORT
Kirtland AFB, NM 87117 NUMBER(S)
12. DISTRIBUTION / AVAILABILITY STATEMENT
Approved for public release; distribution is unlimited
13. SUPPLEMENTARY NOTES
Chemical Physics Letters, Vol. 310, 1999, pp. 111-120
14. ABSTRACT
The rate constant for Cl + HN3 over the temperature range 300 480 K has been studied in a
flow reactor. Based on the rate of loss of HN3 and the rate of NCI(a) generation, the
temperature dependence of this reaction is described by the collision theory expression 1.2
+/- 0.3 x 10A-11 TA0.5 exp(-1514 +/- 93/T), with E(O) = 3.0 +/- 0.2 kcal/mol or an Arrhenius
fit k(T) = 2.0 +/- 1.0 x 10A -10 exp(-1452 +/- 150/T) with Ea = 2.9 +/- 0.2 kcal/mol.
20020905 078
15. SUBJECT TERMS
AGIL, kinetics, C1 atom reactions, HN3, hydrogen azide reactions, temperature dependent rate
constants.
16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON
OF ABSTRACT OF PAGES Gerald C. Manke II
a. REPORT b. ABSTRACT c. THIS PAGE Unlimited 19b. TELEPHONE NUMBER (include area
Unclassified Unclassified Unclassified 14 code)
505-853-2674
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std. 239.18
Reprinted from
CHEMICAL
PHYSICS
LETTERS
Chemical Physics Letters 310 (1999) 111-120
Temperature dependence of the C1 + HN reaction from
3
300 to 480 K
Gerald C. Manke II *, Thomas L. Henshaw, Timothy J. Madden, Gordon D. Hager
Air Force Research Laboratory, AFRL /DELC, 3550 Aberdeen Avenue SE, KirtlandA FB, NM 87117-5776, USA
Received 10 May 1999; in final form 28 June 1999
NH
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CHEMICAL
PHYSICS
LETTERS
ELSEVIER Chemical Physics Letters 310 (1999) 111-120
www.elsevier.nl/locate/cplett
Temperature dependence of the C1 + HN reaction from
3
300 to 480 K
Gerald C. Manke II *, Thomas L. Henshaw, Timothy J. Madden, Gordon D. Hager
Air Force Research Laboratory,A FRL/DELC, 3550 Aberdeen Avenue SE, KirtlandAFB, NM 87117-5776, USA
Received 10 May 1999; in final form 28 June 1999
Abstract
The rate constant for Cl + HN over the temperature range 300-480 K has been studied in a flow reactor. Based on the
3
rate of loss of HN and the rate of NCI(a'A) generation, the temperature dependence of this reaction is described by the
3
collision theory expression 1.2 + 0.3 X 10-1" T0.5 exp(- 1514 + 93/T), with E, = 3.0 ± 0.2 kcal mol-1 or an Arrhenius fit
k(T) = 2.0 ± 1.0 X 10-10 exp(- 1452 + 150/T) with E., = 2.9 ± 0.2 kcalmol-. © 1999 Elsevier Science B.V. All rights
reserved.
1. Introduction used for the generation of NCI(a'A) is summarized
by reactions (1) and (2):
The recent report of a direct measurement of gain
[1] on the I(-p1/2- 2P3/2) transition in the Cl + HN3 - HCl + N3
NCI(a'A)/I chemical system has increased interest C + N3 - NCIaA, b X 31) + N2 (2)
in the use of metastable nitrene halides (NX) as
energy donors for iodine-based chemical lasers anal- The A H0° value for reaction (1) is -9.3 kcal mol-1,
ogous to the chemical oxygen iodine laser (COIL) and the enthalpy for reaction (2) is -39, - 22, and
[2,3]. There are several important advantages and -65 kcal mol'- for generation of the (a'A), (b'l +
disadvantages to the use of these molecules, which and (X3 ý- ) states, respectively, using A H1°(NC1) =
are isovalent with 02. The most obvious advantage 77.4 kcalmol-' [14]. The rate determining step for
is generation of the (a1A) states in the gas phase this process is reaction (1), which has a room tem-
[4-10] rather than the mixed gas/aqueous chemistry perature rate coefficient [15] of 1.1 ± 0.3 X 10-12
that is necessary for COIL operation. On the other cm3 molecule' s- 1. Gain on the I(2p3/2)-I*(2 P1/2)
hand, the NX(a'A) molecules are much more reac- transition was achieved when a small flow of HI is
tive than 0 (a6A) [11-13], and the scaling issues for added to a flow of NCI(a'A):
2
generating high concentrations of NCI(a'A) have not
yet been resolved. The C1/HN3 chemical system Cl + HI - HC1 + I(2P3/2) (3)
NCl(al1A) -+-I(-P3/2) -'- NCI(x 3](cid:127)-) +'- I (P,2)
* Corresponding author. Fax: + 1-505-846-4807; e-mail: (4)
(4)
[email protected]
0009-2614/99/$ -see front matter © 1999 Elsevier Science B.. All rights reserved.
PIH: S0009-2614(99)00726-5
114 G. C. Manke II et al. / Chemical Physics Letters 310 (1999) 111-120
0.2
0 300K
o 458K
0.0 - linear regression
-0.2
00
z -0.4
-0.6
-0.8
-1.0
0.000 0.005 0.010 0.015 0.020 0.025 0.030
At (seconds)
Fig. 2. Pseudo-first-order plots of In I/Io(NH(A 3 Hl)) versus reaction time. The experimental conditions and results are as follows: (300 K)
[Cl] = 1.2 X 1013, [HN,] = 2.0 X 1012 cm-3, k = 1.4 ± 0.1 X 10-12 cm3 molecule' s-1; (373 K) [CI] = 8.0 ×1 012, [HN3] = 3.0 X 1012
cm-3, k = 4.5 ± 0.3 X 10- 12 cm3 molecule- I s-; (413 K) [C1] = 6.0 x 1012, [HN3] = 2.8 X 10 12 cm-3, k = 6.5 0.4 X 10-12
cm3 molecule 1 s- 1; (458 K) [Cl] = 6.0 X 1012, [HN3] = 1.7 x 1012 cm-3, k = 8.5 ± 0.3 X 10- 12 cm3 molecule' s- 1.
CF I in 12 L bulbs. The flow rate of HCl was stored in a stainless steel vessel. HN was added to
3 3
determined by diverting the stream to a vessel of the reactor via one of two sliding Pyrex injectors.
known volume and measuring the rate of pressure The entire reactor was encased by resistive heat-
rise. The bulk of the flow (typically 2.5 SLPM, 1850 ing units, which consisted of Nichrome wire heli-
p m s- 1) consisted of Ar (Airgas, UHP grade). Two cally wound inside a ceramic jacket. The temperature
microwave discharges on a CF (Airgas, 99.5%)/Ar was measured by inserting several type K thermo-
4
mixture produced up to 1.5 X 1013 cm-3 F atoms at couples into the gas stream at various points along
1.5 torr. Pre-prepared mixtures of HN and He were the reactor. A flexible thermocouple was inserted
3
Table 2
S. ..... nf the. k(T) measurements via loss of -N3
G.C. Manke H et al. / Chemical Physics Letters 310 (1999) 111-120 115
into the one of the movable injectors to provide a A 0.3 m monochromator (Instruments S.A.) dis-
temperature measurement at the center of the tube. persed the chemiluminescence collected by a short
The heaters were regulated with Omega controllers focal length lens. Two different gratings (500 or 900
(Model CN76000) with an accuracy of + 10 at room nm blaze, both with 1200 grooves mm-1) were used,
temperature and + 70 at 480 K. All inner surfaces depending on the emission of interest. The emissions
were coated with PTFE, which limited the tempera- of HF (Av = -3), NF(Wa A), NCI(a 'A), NF(b 11+),
ture to 500 K. and NCI(bIl÷) were monitored with a cooled
0.152
T= 300 K
E
C-)
20.10 53'
S5k=, o3 0
1.0 x 10-12 cm3 molec"1 s"1
S0.05 X
Z
k = 3.0 x 10-12 cm3 moleo4 s1
0.00 , 0
0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.040
At (seconds)
0.20
T= 388 K
1.5
0.15 -E
Q
, 1.0 -1
"01 k5O 10 cma molee4 s4 E
k--(cid:127) \ k = 3.0 x 10012 cm3 molec"1 s"1 0
Z'Z)0.105 - E
0,5
k = 7.0 x 10 cm molec1 s`-- "
0.00 0.0
0.000 0.005 0.010 0.015 0.020
Fig. 3. Non-pseudo-first-order plots of I(NH(A 3H) versus reaction time. A least-squares fitting routine was used to extract k from the
dLaotwa.e rT hpea neexl:p eTrim= e3n8ta8l Kco, n[dCi1ti]o =ns 6 .a5r e Xa s1 0fo12ll;o w[Fs] . =U p1.p5e rx p1a0n1e2l:; T[H=N 33]0 0= K1.,5 [XCl ]1 0=1 21 .1c mX- 310. "3N, o[tFe] =th a2t .0th Xe 1d0a"t2a , c[aHnN 3be] = s a2ti.s0f aXc to110r 1il2y cfmit -b3y.
several values for k, and the relative error for this method is large.
116 G. C. Manke 1 et al./ Chemical Physics Letters 310 (1999) 111-120
(- 80°C) R1767 PMT (Hamamatsu) while the UV PMT) from the reaction of F and Cl atoms with HN
3
emission from NH(A31H) was detected with a R374 is shown in the upper panel of Fig. 1.
PMT (Hamamatsu) cooled to - 50TC. When neces- The relative concentration of HN was monitored
3
sary, band pass or long pass filters were used to by adding N (A31,) via the indicator inlet and
2
isolate signals of interest from unwanted background monitoring the resultant NH(A 3 H-) signal at 335 nm.
or second-order emissions. A representative spec- The N (A 31,) molecules were generated by energy
2
trum (uncorrected for the relative response of the S-1 transfer from metastable Ar(3P , 3Po) atoms using a
2
2.5e+12
T = 300K = 1.6 x 10-12 cm3 molec"1 s-1
S2.0e+12
1
E k, 1.0 x 10"12 cm3 molec1 s" - -
0 1.5e+12 -
E
1.0e+12
,i =88.6 xx1k0 "3 cm3 molece s-1
;Zý 5.0e+11 . "
/Z k = 5.0 x 10 3 cm molec s
0.0,
0.00 0.01 0.02 0.03 0.04
At (seconds)
1.5e+12
T = 433K k, = 8.4 x 10"12 cm3 molec"1 s" ki = 5.9 x 10-12 cm3 molec"' s-1
: 1.2e+12 _
E
o k, 1.1 x 10-11 cm3 molec1 s"1 IL
S9.0e+11
E
6.0e+11 k= 3.4 x 101"0 12 Ccm3 molec"11 .s-1
Z 3.0e+11
0.0
0.000 0.005 0.010 0.015 0.020 0.025
At (seconds)
Fig. 4. Measurement of k, via generation of NC1(a 'A). A least-squares model fit to [NCI(a A)] versus At was used to determine
k(Cl + HN3). The experimental conditions are as follows. Upper panel: T = 300 K, [CI] = 1.8 X 10"3, [HN3] = 2.0 X 10" cm-3.Lower
panel: T= 433 K, [Cli = 8.0 X 10"2, [HN = 1.4 X 10'3 cm-3.Note that a wide range of values for k, can satisfactorily fit the data, and
3
the relative error for this method is large (± 30%).
G. C. Manke 11 et al. / ChemicalP hysics Letters 310 (1999) 111-120 117
rolled tantalum foil discharge design [21]. The described above and the error bars for k, are signifi-
NH(A3Hf) emission intensity increased linearly with cantly larger. Table 2 summarizes the k(T) data for
the HN flow rate (see the lower panel of Fig. 1). reaction (1) based on the loss of [HN ].
3 3
With optimization of the light collection and
N2(A3I-') generatorU, [HN33].2 . as low as 1 x 10'o Generation of NCl(a )
3
moleculecm-3 could be routinely detected even
Sth ough the branching ratio to (5b) is low. The rate determining step for the generation of
NCI(a'A) is reaction (1). For nearly any set of
3. Results and discussion conditions where no [F] is present, the rate of
NCI(a'A) growth is dependent upon k,. Fig. 4 shows
3.1. Monitoring the loss of [HN, ] several examples of the growth of NCI(a 'A) versus
At at a variety of temperatures. In each case the
Under pseudo-first-order conditions ([Cl] >> linear least-squares fit to the data is indicated by the
[HN ]) the slope of a given ln(I(NH(A3H)) versus solid line, while alternate values for k, are shown by
3
At plot is equal to k,[Cl], and the rate constant is broken lines. As expected, the established value for
given by simply dividing by the known [Cl]. Measur- k, is reproduced at room temperature. However, the
able decomposition of HN does not occur below precision of this method is quite poor. As the plot
3
560 K and reactive loss should be the only removal shows, several values, up to + 30%, also give rea-
process [22]. Fig. 2 shows several such measure- sonable fits to the data. This method is also suscepti-
ments taken at a variety of temperatures. In each ble to error in other ways. For example, as k,
case, the initial [Cl]0 was determined by first measur- increases the value of k2(T) (which was fixed to the
ing [F] and then adding a slight excess of HC1. The room temperature value) becomes more important
0
intensity decreased with time, and a regression fit to because N3 and UN3 compete for reaction with [Cl].
the data gives the product k,[C1]. At room tempera- Most importantly, it is difficult to generate observ-
ture, the data is within the combined error bars of the able I(NCI(a 'A)) without high [Cl]0 and [HN3]0,
established value for k,, 1.1 + 0.3 10-12 which may cause additional problems with quench-
cm3 molecule' s-1. Several measurements were ing. Although this method is less satisfactory for the
determination of kj, the results agree quite well with
performed at each temanpde2rae stvuanrietd iroadns d aT aeblaeh 2 tlmistps etah-e dtheotsaein obtainedo f by mmonointiotrhirnegtg I(NiHte( A3 wH )) el(see
average and 2 standard deviations at each tempera-3).
ture. The value of k, increases up to 1.1 + 0.1 X Al 3).e
10-'"c m3 molecule-1 s'-' for T = 460 K. All of the k(T) data for reaction (1) are summa-
Because HCI quenches N2(A31,) (kQ = 1.3 x rized in Tables 2 and 3 and in Fig. 5. A least-squares
10-12 cm3 molecule-' s-') [231, it was not always
possible to add excess HC1 and a few measurements
of k, were performed with a mix of F and Cl atoms
present with HN . A known flow of HC1 is added to Table 3
aar eamsueeadst ured [[FF]],,, ,3 aanndd [[FF]]"" oaanndd fl[[oC w1]f'C cc ai lcuallasc t ede dff rroomm STumkmTary of the k(T) measurements via generation of NCI(a A)
tohfe [HbNim]o,l eacsu mlaor nriatoter edla wb.y TI(hNe Ht(eAm p3oHraI)l), dise fpiet nbdye nthcee T(K ) k(x(T i) 0-'t cm3 molecule- ' s- i)
kinetic 3model listed in Table 1. In cases such as 333080 00..889 ±±0 0..827
338 2.6±0.8
these, accurate measurement of k, requires [Cl] >> 368 3.4+ 1.0
[F], and [F] < [HN ]0. Otherwise, F removes nearly 383 4.8+1.4
3
all of the HN3 and it becomes impossible to accu- 388 5.8+ 1.7
rately extract k, [5]. Several examples are shown in 403 7.7+2.3
Fig. 3. In each case, the least-squares analysis pro- 433 8.4±2.5
448 9.3_+2.8
duces a satisfactory fit to the data. This method, 468 11±+3
however, is inherently less sensitive than the method
118 G.C. Manke H et al. / Chemical Physics Letters 310 (1999) 111-120
-22
Arrhenius fit:
k(T) = 2.0 x 10 e "1452RT
-23 Ea = 2.9 kcal mol"1
-24
o-25
0E) -26
E
"-27
_ -28.
"*
removal of HN
3
-29 -A estimate from ref. 1
"* NCI(a1A) growth
- Arrhenius fit
-30
1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00
1000iT (K1)
-22
Collision Theory fit:
k(T) = 1.2 x 10.1 T°'Se1s6141r
-23 -E0= 3.0 kcal mol"1
-24
o -25
0)
o, -2
E
27 --
-: -28 "*
removal of HN
3
-29 -A estimate from ref. 1
"* NCI(a1A)g rowth
-- collision theory fit
-30
1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00
1000/T (K1)
Fig. 5. Arrhenius and collision theory fits to the kl(T) data. Upper panel: The k,(T) data is fit by the Arrhenius expression. The best fit is
achieved for A = 2.0 X 10-1° and Ea = 2.9 kcalmol-1. Lower panel: A collision theory expression is used and A = 1.2 X 10-1 and
E, = 3.0 kcal mol - 1. In both panels data from both the loss of HN and generation of NCl(a 'A) techniques are shown.
3
analysis of the data using the collision theory expres- from the data reported in Ref. [1], and excellent
sion, AT('5 exp(-Eo/RT), results in a satisfactory agreement is achieved.
fit with A=1.2±0.5X10-1' and E =3.0±0.3
0
kcal mol - . The Arrhenius expression was also used 4 Discussion
to fit the data: k(T) = 2.0 ± 1.0 X 10-10 exp(- 1452
± 150/T) with E, =2.9 ± 0.3 kcalmol-1. The data While several azide/atom (F, Cl, and H) reac-
in Fig. 5 also includes an estimate for k, calculated tions have been characterized at room temperature,
G. C. Manke II et al. / Chemical Physics Letters 310 (1999) 111-120 119
there have been few measurements for T > 300 K. and requires some comment. Hydrogen atom abstrac-
For example, reaction (7) tion reactions such as F + HC1 (k = 4.4 + 1.5 X
0- exp( - 400 + 100/T) cm3 molecule -1 s -1)
2 F + HN3 (cid:127)HF + N3 - HF + NFWaIA) + N2 28] and Cl + HBr (k =4.8 X 10-11 exp(-454/T)
(7a) cm3 molecule- 1 s- 1) [29] have A factors which are
~ 2-3 smaller than the present result. Halogen atom
- HNF + N2 --* HF + NF(a 'A) + N2 addition reactions, on the other hand, typically have
(7b) much larger pre-exponential factors. For example, a
relevant comparison may be made with the fast
is known to be an efficient source of the N and reaction F + HN , A > k = 1.1 + 0.2 X 10-10
3 3 300
NF(a 'A) radicals. The room temperature rate con- cm3 molecule' s-1. Chlorine atoms are known to
stant [5] for (7a) is established as 1.1 + 0.2 X 10- add to olefins (e.g., C H [30], C H Br [31, and
2 4 2 3
cm3 molecule-l s - and the nascent HF vibrational C H C1 [32]) and these reactions are very fast at
2 3
distribution from reaction (7a) is 0.36:0.36:0.22:0.06 room temperature, 0300) = 1.5 ± 0.4 X 10-'0
for v = 1-4. Microscopic branching between direct cm3 molecule- 1 s- 1. The Cl + olefin reactions also
abstraction and addition-elimination channels may have very small activation energies, probably on the
account for the rather flat vibrational distribution, order of a few hundred calmol-1. For example,
The branching to HNF (7b) has been established [24] assuming Ea 0.3 kcal mol-, and using k (C1 +
as 0a.0s3..".0+.00.0021 . The rate coefficient for the reaction of CC2sHH3mBrn) rE= =1 1.4.33 ±± 00..22 9 X 1100-11°0 uccmi3 mo2l9e8cule-'
Hto a4to6m0 s Kw itahn dH Nk3( Th)a=s 2b.5e×enlO m1-e asu'r'eexd p[(2-5 ] f2ro3m15 /3T00) ss -th', the A ffaactrt2o"r ×is1 -2c.m4 mX lu1e0--- " cm3 molecule
t 4Clearly, the large pre-exponential factor for Cl + HN
3
cm3 (m olecuVle 2 s- The reaction produces is consistent (i.e., within a factor of 2-3) with other
NH (2A , v < 20) [26] and minor amounts of Cl atom reactions and is suggestive of a Cl atom
2 1 2
NH(A3 H1)a nd NH(b '). addition reaction rather than hydrogen abstraction.
H + HN3 - NH2 + N2 (8a) The main products for reaction (1) are assumed to
be HC1 and N even though vibrationally excited
The mechanisms wfolr) NH(A3 and Nt H(bt HC1 has not b3e en observed (only HCI(v = 1) is
production are not well established, but they are energetically possible) and the generation of HNC1
prsumed to b: gcannot be ruled out. Independent confirmation of this
such as [26]: could be accomplished in one of several ways:
H + HN3 -- N3 + H2 (8b) laser-induced fluorescence detection of N3 or in-
frared absorption of HCl(v = 0, 1) generated by reac-
H + N3 - NH(b 1Z) + N2 (9) tion (1) are the most easily implemented. Virtually
2NH* (b V a'A) -- NH(A3fI) (10) nothing is known about the species HNC1. If one
assumes that Cl + HNC1 is sufficiently exothermic to
Prior to this report, the only halogen/azide reaction give NCI(a 'A), by analogy to the F + HN system,
3
that had been characterized T> 300 K was Cl + both N and HNC1 should react rapidly with Cl
3
CIN : atoms to give NCI(a 'A).
3
Cl + CIN3 - N3 + C12 (11)
Combourieu et al. used mass spectrometric detection
to measure the temperature-dependent rate constant 5. Conclusions
between 300 and 657 K [27]. They reported a moder-
ate temperature dependence of k(T) = 2.3 X The temperature dependence of the reaction Cl +
10-'' exp(- 554/T) cm3 molecule-' s- 1. HN has been measured in a heated flow reactor.
3
The present results indicate a moderate tempera- The rate coefficient was measured by monitoring the
ture dependence for the reaction of Cl + HN , with loss of HN and the rate of generation of NCI(a 'A)
3 3
E, = 3 kcal mol- 1. The pre-exponential factor is large versus time for known starting concentrations. The