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On the dynamics of the ion-pair state of Cl2 in the presence of inert gases
Voiume 112, number 4
CHEhliCAL
ON THE DYNAMICS OF THE ION-PAIR
STATE OF Cl, IN THE PBSENCE
Takashi ISHIWATA,
and Ikuzo TANAKA
Atsuto TOKUNAGA
14 December 1984
PHYSICS LETTERS
OF INERT GASES
Departrnent of Clzemistry, Tokyo Iwittcte of Technology, Ohokayama. hfeguro, Tohyo 25.2. Japan Received 16 August 1984
We have observed ultraviolet fluorescence spectra of Cl+ert gas mixtures following one-photon resonam three-photon exciterion of Cl2 10 zhe ‘t-* . Ic Ion-pair state. XeCl emission appeared at 308 nm in the presence of Xe, while coliksionai relaxation 10 the lowest lying E(C@ ion-pair state was found to be ~om~a~l in the presence of He, Ar, and Kr. The rate constant for XeCI formation was determined to be (3.0 + 0.5) X lo-" cm3 molecufe-l s-l_
1. Introduction During recent years, several methods which utilize sequential multiphoton transitions havebeen developed to investigate the spectroscopic properties of the electronically excited states of halogen molecules [l-S]_ The method used in this laboratory for the study of ion-pair states is optics-optical double resonance (OODR), where the molecuIes are excited through the intermediate B 311(Oi> state f6-IO]. We have shown that this method makes it possible to probe these excited states with the inversion symmetry (parity) identical or opposite to that of the X ‘ISi ground state, depending on whether the total number of photons absorbed is even or odd. The stepwise process compromises the large Franck-Condon shift required to excite the molecules to the lower vibrational levels of the ion-pair states. The study on the dynamics of Cl, ion-pair states has been stimulated by the laser action demonstrated on the 258 mn emission band [ 1 I] _ Recent experiments show that the quenching processes involve interstate transfer remiinating on the lowest E(Oi) ion-pair state [12,13] and the laser emission is now attributed to the E(Oi)-B 3n(Oi) transition [S,l4, 151. Furthermore, the presence of the reactive channel for the ion-pair states giving the KrC1 and XeCl
excimer emissions is indicated [ 131. The purpose of this paper is to report preliminary results on the dynamics of Cl2 ion-pair state employing one-photon 356
resonant three-photon absorption through B “II state. The complete selectivity of the excitation permits us to follow relaxation processes of the ion-pair stable by measuring fluorescence spectra.
2. Experimental The experimental apparatus used in this study was the same as described previously f63 _ The chlorine molecules were excited to the ‘CG ion-pair state by focusing radiation from a nitrogen laser pumped dye laser (Molectron UV-24/DL14). UV fluorescence from a sample cell containing Cl%/inert gas mixtures was observed at right angles to the laser beam and dispersed by a 50 cm monochromatorThe signals from a photomultiplier (Hamamatsu TV R-166UH or lP-28) were amplified ten times and averaged by a boxcar integrator (PAR 105/162/164).
3. Results and discussion
Fig. 1 shows a typical example of emission spectra obtained when the Cl-, molecules are excited to the 1x; ion-pair state in the presence of Xe. The laser frequency is adjusted to a photon energy of 19924.7 CII?-' Which gives rise to one-photon resonant threephoton excitation of Cl,,
0 009-~614/84~$03.00 0 Elsevier Science Publishers snort-Holl~d Phvsics Publishing Division)
B-V.
V&me
112, number 4
14 December 1984
CHEBiIC.L\LPHYSICS LEiTEiG
r
Cl, = 5.2
Torr
Xe = 28.3 Torr
2i)o Wavelength
2til (nm)
Fig. 1. Emission spectrum of C12/Xe mixture when the Cl* molecules are exited to the ‘x’, state by a one-photon resonant three-photon excitation.
211Y
11Y
X1X;: B ‘II@;) = (17-O) P(11) -
-
(O-12) QUO)
5;.
(1)
As discussed in the previous publication 161, the spectrum exhibits two types of fluorescence band originating from the lZ= ion-pair state. (1) A system with a vibrational structure at around 235 MI corresponding to a transition terminating on the X 1X; ground state. (2) A broad band system with an intensity maximum at around 259 nm which is a boundfree emission having a repulsive state correlating with
C1(2P) i- C1(2P) as a lower state. Aside from these Cl, bands, the XeCl excimer emission from the B and C states appeared at 308 and 340 nm, respectively [ 161. The band profile at 308 nm showed the vibrational relaxation in the XeCl(B) state even for total pressures as low as 10 Torr. Since Xe itself is transparent at the laser wavelength employed here, the excitation spectrum of XeCl emission showed the same structure as that of the Cl;! band systems. This result rules out the photoassisted reaction of Xe with Cl, to form XeCl* [17-191 in our case. Under the condition that a constant pressure of Cl2 were used, the increase of Xe pressure resulted in an increase of XeCl emission and a decrease of Cl, emission, while the total fluorescence intensity was iridependent of the Xe pressure up to 50 Torr. The emis-
sion intensities of the Cl? and XeCl bands increased almost linearly with an increase of Cl, partial pressure and showed the same second-order dependence on laser power. Therefore, the consequence of the XeCl emission is immediately clear. The primary three-photon excitation of Cl, leads to the formation of XeCl excimer. For a quantitative understanding of the XeCl and Cl, emission intensities, we assumed the following reaction schemer Cl; + Xe + XeCl’ + Cl,
(2)
Cl? -?. Cl2 -I-hUI ,
(3)
XeCl* + XeCl + burr )
(4)
where the collisional quenching of XeCl* and Cl*, is neglected. Process (4) effectively denotes the radiative decay of the coupled B and C states. The rate equation for the total XeCI* population could be expressed as -d[XeCl*]/dt
= -k?[Xe]
[Cl;] + k4 [XeCI*] _
(5)
Time integration of eq. (5) gives the integrated populations of Cl; and XeCl*, which are easily converted to the relation of the total XeCl and Cl, emission intensities, IX&l *&,;
= (kJk&[Xe]
_
(66) 357
CHEMICAL
Volume 112, number 4
XeCl* according to eq. (6); II-, = (3.0 f 0.5) X IO-10 cm3 molecule-1 s-l. Reaction (2) is exothermic by 20.3 kcal/mol and has a large reaction rate constant comparable with the metastable rare-gas collision channel for the XeCl* formation (x’xecI* = 7.2 X 10VIO cm3 molecule-l s-l),
0
20 .
._
I’
t5-
.
_
8:
5; 1 3 al x
4
l
lxx
,’
10
/-
5
-
a;.
xe -
XeCi
+ Cl
ii 0’
0
50
200
I50
100 xe
pressure
(TorrJ
Fig. 2. Emission intensity ratio (XeCI*/CI~) the Xe pressure_
as a function of
Fig. 2 summarizes the experimental results on measured fluorescence ratio as a function of Xe pressure. It is clear that the intensity ratio increases linearly with an increase of Xe pressure as expected from eq. (6) and we confirmed it to be independen of Cl, pressures lower than 6 Torr. The curvature observed above 50 Torr Xe pressure exhibits the quenchmg of XeCI* by Xe_ We have measured the fluorescence lifetime of the ‘Zz state of CI?, which was found by a deconvolution method to be 14 i 2 ns at 0.05 Torr Cl,. The pressure is low enough to exclude the probability of removal by collisions and we used this value to calculate the rate constant for the collisional formation of
260
Fig. 3. Emission spectrum of resonant three-photon
358
the E(O&B excitation
Xe*(3P,)
+ Ci, + XeCl* + CI _
(7)
A large collisonal cross section of the excited species is expected from a long-range harpooning mechanism, where the input and exit channels are coupled by an intermediate ion-pair potential curve. It is likely that the reaction surface of the Cl, ‘Zz ion-pair state with Xe might cross with the ion-pair potential (Xe’-Cl,) whose exit channel is XeCl* + Cl just as for reactive quenching of Xe metastable atoms 1201. This assumption is consistent with results of a two-photon assisted reaction of Xe with Cl,, in which Xe and Cl2 might be directly excited to a Teactive channel of the same type as in this study, giving a broad excitation spectrum for the XeCl emission at 308 mn [ 191. With the addition of He, Ar, or Kr, the Cl2 emission bands also decreased in intensity associated with a change of their profde. Fig. 3 is the fluorescence spectrum of an Ar/CIZ mixture excited at 19924.7 cm-l. Under this high-pressure condition, the lZi-lZl fluorescence obviously disappeared. The 258 nm band is now the dominant fluorescence channel, which can be attributed to the E(Oi)-3 %(OS) transition. This result agrees with the previous observations; the E-B
250 Wavelength
photon
14 December 1984
PHYSICS LETTERS
Cl2
: 3.1
Torr
Ar
:
~orr
120
210
230
(nm)
3n(Oz) system observed when the (212 molecules are exited in the presence of AI.
to the lx:
state by a one-
Volume
112, number 4
CHEMICAL
PHYSICS LETTERS
fluorescence could be developed in the electronic dischange and e-beam pumping experiments by admixing unreactive inert gases such as He and Ar to Clj. The E(O> state might be the lowest state among the twenty ion-pan states correlating with Cl-(lS) + Cli+(3P, lD, IS). Collisional interstate transfer terminating on the lowest E(Oi) state obviously completes the deactivation process in the upper ion-pair states. These processes are closely related with the detailed mechanism of Cl, laser at 258 mn.
References
t11 G.W.
King, 1-M. Littlewood and JR. Robins, Chem. Phys. 56 (1981) 145; J.P. Perrot, M. Broyer, J. Chevaleyre and B. Femelt, Chem. Phys. 67 (1982) 59; J. Mol. Spectry. 98 (1983) 161; J.B. Koffend, R. Basis, M. Broyer, J-P. Pique and S. Chummy, Laser Chem. l(1983) 343. f21 J.C.D.Brand,A.R.Hoy,A.K.KalkerandA.B.Yamasbita. J. Mol. Spectry. 95 (1982) 350; J.C.D. Brand and A.R. Hoy, J. Mol. Spectry. 97 (1983) 379. [31 F.W. Dalby, G. Petty-S& M.H.L. Pryce and C. Tai. Can. J. Phys. 55 (1977) 1033; K-K. Lehmann, J. Smolarek and L. Goodman, J. Chem. Phys. 69 (1978) 1569; D.E. Cooper and J-E. Wessel, J. Chem. Phys. 76 (1982) 2155. [4] C. Tai. F-W. Dalby and G.L. Giles. Phys. Rev. 20 (1979) 233. [5] K. Chen. L-E. Steenhoek and E.S. Yeung, Chem. Phys. Letters 59 (1978) 222.
14 December
1984
[6] T. Ishiwata, I. F ulrwara -_ and L Tanaka, Chem. Phys. Letters 89 (1982) 527. [7] T. Ishiwata, I. Fujiwara, T. Shinzawa and T_ Tanaka, J_ Chem. Phys. 79 (1983) 4779. [8] T. Ishiwata and 1. Tanaka, Chem. Phys. Letters 107 (1984) 434. [9] T. Shinzawa, A. TokunaSa, T. Ishiwata, I. Tanaka, K. Kasatani, hi. Kawasaki and H. Sato, J. Chem. Phys. 80 (1984) 5909; T. Isbiwata, H. Ohotoshi and L Tanaka, J. Chem. Phys., to be published. [lo] T. Ishiwata, H. Ohotoshi, M. Sakaki and I. Tanaka, J. Chea Phys. 80 (1984) 1411. [ 1 l] C-H. Chen and M.G. Payne, AppL Phys. Letters 28 (1976) 219; AK. Hoys, Opt. Commun. 28 (1979) 209; hL Diegelmann, K Hohla. F_ Rebentrost and KJKompa, J_ Chem Phyr 76 (1982) 1233. [ 121 MC. Castex, J. Le Calv& D. Haaks, B. Jordan and G. Ziiner, Chem Phyr Letters 70 (1980) 106; Nuovo Cimento B63 (1981) 265. [ 131 M.W. Wilson, R Rothschild and C-K Rhodes, J. Chem. Phys. 78 (1983) 3779. [14] S-D. Peyerimhoff and RJ. Buenker, Chem. Phys. 57 (1981) 279. [ 151 E. Schatzlein, W. Walter, R. Sauerbrey and H. Langhoff, Appl. Phys B27 (1982) 49. [16] J-H. Kolts, J-E. Velazoco and D-W. Setser, J. Chem. Phys. 71 (1979) 1247. [ 171 VS. Dubou, L.E. Gundzenko, L-U. Gurovich and S. Iakovlenko. Chem Phys. Letters 53 (1978) 170; VS. Dubou, V.E. Lapsker, A.N. Samoilova and V-A. Gurvich, Chem. Phyr Letters 83 (1981) 518. [18] B.E. Wilcomb and R. Bumham, J. Chem. Phys. 74 (1981) 6784. [ 191 J-K. Ku, G. Inoue and D-W. Setser, J. Phys. Chem 87 (1983) 2989. [ 201 J-E. Velazazco, J.H. Kolts and D-W_ Setser, J. Chem. Phys. 69 (1978) 4357.
359
CHEhliCAL
ON THE DYNAMICS OF THE ION-PAIR
STATE OF Cl, IN THE PBSENCE
Takashi ISHIWATA,
and Ikuzo TANAKA
Atsuto TOKUNAGA
14 December 1984
PHYSICS LETTERS
OF INERT GASES
Departrnent of Clzemistry, Tokyo Iwittcte of Technology, Ohokayama. hfeguro, Tohyo 25.2. Japan Received 16 August 1984
We have observed ultraviolet fluorescence spectra of Cl+ert gas mixtures following one-photon resonam three-photon exciterion of Cl2 10 zhe ‘t-* . Ic Ion-pair state. XeCl emission appeared at 308 nm in the presence of Xe, while coliksionai relaxation 10 the lowest lying E(C@ ion-pair state was found to be ~om~a~l in the presence of He, Ar, and Kr. The rate constant for XeCI formation was determined to be (3.0 + 0.5) X lo-" cm3 molecufe-l s-l_
1. Introduction During recent years, several methods which utilize sequential multiphoton transitions havebeen developed to investigate the spectroscopic properties of the electronically excited states of halogen molecules [l-S]_ The method used in this laboratory for the study of ion-pair states is optics-optical double resonance (OODR), where the molecuIes are excited through the intermediate B 311(Oi> state f6-IO]. We have shown that this method makes it possible to probe these excited states with the inversion symmetry (parity) identical or opposite to that of the X ‘ISi ground state, depending on whether the total number of photons absorbed is even or odd. The stepwise process compromises the large Franck-Condon shift required to excite the molecules to the lower vibrational levels of the ion-pair states. The study on the dynamics of Cl, ion-pair states has been stimulated by the laser action demonstrated on the 258 mn emission band [ 1 I] _ Recent experiments show that the quenching processes involve interstate transfer remiinating on the lowest E(Oi) ion-pair state [12,13] and the laser emission is now attributed to the E(Oi)-B 3n(Oi) transition [S,l4, 151. Furthermore, the presence of the reactive channel for the ion-pair states giving the KrC1 and XeCl
excimer emissions is indicated [ 131. The purpose of this paper is to report preliminary results on the dynamics of Cl2 ion-pair state employing one-photon 356
resonant three-photon absorption through B “II state. The complete selectivity of the excitation permits us to follow relaxation processes of the ion-pair stable by measuring fluorescence spectra.
2. Experimental The experimental apparatus used in this study was the same as described previously f63 _ The chlorine molecules were excited to the ‘CG ion-pair state by focusing radiation from a nitrogen laser pumped dye laser (Molectron UV-24/DL14). UV fluorescence from a sample cell containing Cl%/inert gas mixtures was observed at right angles to the laser beam and dispersed by a 50 cm monochromatorThe signals from a photomultiplier (Hamamatsu TV R-166UH or lP-28) were amplified ten times and averaged by a boxcar integrator (PAR 105/162/164).
3. Results and discussion
Fig. 1 shows a typical example of emission spectra obtained when the Cl-, molecules are excited to the 1x; ion-pair state in the presence of Xe. The laser frequency is adjusted to a photon energy of 19924.7 CII?-' Which gives rise to one-photon resonant threephoton excitation of Cl,,
0 009-~614/84~$03.00 0 Elsevier Science Publishers snort-Holl~d Phvsics Publishing Division)
B-V.
V&me
112, number 4
14 December 1984
CHEBiIC.L\LPHYSICS LEiTEiG
r
Cl, = 5.2
Torr
Xe = 28.3 Torr
2i)o Wavelength
2til (nm)
Fig. 1. Emission spectrum of C12/Xe mixture when the Cl* molecules are exited to the ‘x’, state by a one-photon resonant three-photon excitation.
211Y
11Y
X1X;: B ‘II@;) = (17-O) P(11) -
-
(O-12) QUO)
5;.
(1)
As discussed in the previous publication 161, the spectrum exhibits two types of fluorescence band originating from the lZ= ion-pair state. (1) A system with a vibrational structure at around 235 MI corresponding to a transition terminating on the X 1X; ground state. (2) A broad band system with an intensity maximum at around 259 nm which is a boundfree emission having a repulsive state correlating with
C1(2P) i- C1(2P) as a lower state. Aside from these Cl, bands, the XeCl excimer emission from the B and C states appeared at 308 and 340 nm, respectively [ 161. The band profile at 308 nm showed the vibrational relaxation in the XeCl(B) state even for total pressures as low as 10 Torr. Since Xe itself is transparent at the laser wavelength employed here, the excitation spectrum of XeCl emission showed the same structure as that of the Cl;! band systems. This result rules out the photoassisted reaction of Xe with Cl, to form XeCl* [17-191 in our case. Under the condition that a constant pressure of Cl2 were used, the increase of Xe pressure resulted in an increase of XeCl emission and a decrease of Cl, emission, while the total fluorescence intensity was iridependent of the Xe pressure up to 50 Torr. The emis-
sion intensities of the Cl? and XeCl bands increased almost linearly with an increase of Cl, partial pressure and showed the same second-order dependence on laser power. Therefore, the consequence of the XeCl emission is immediately clear. The primary three-photon excitation of Cl, leads to the formation of XeCl excimer. For a quantitative understanding of the XeCl and Cl, emission intensities, we assumed the following reaction schemer Cl; + Xe + XeCl’ + Cl,
(2)
Cl? -?. Cl2 -I-hUI ,
(3)
XeCl* + XeCl + burr )
(4)
where the collisional quenching of XeCl* and Cl*, is neglected. Process (4) effectively denotes the radiative decay of the coupled B and C states. The rate equation for the total XeCI* population could be expressed as -d[XeCl*]/dt
= -k?[Xe]
[Cl;] + k4 [XeCI*] _
(5)
Time integration of eq. (5) gives the integrated populations of Cl; and XeCl*, which are easily converted to the relation of the total XeCl and Cl, emission intensities, IX&l *&,;
= (kJk&[Xe]
_
(66) 357
CHEMICAL
Volume 112, number 4
XeCl* according to eq. (6); II-, = (3.0 f 0.5) X IO-10 cm3 molecule-1 s-l. Reaction (2) is exothermic by 20.3 kcal/mol and has a large reaction rate constant comparable with the metastable rare-gas collision channel for the XeCl* formation (x’xecI* = 7.2 X 10VIO cm3 molecule-l s-l),
0
20 .
._
I’
t5-
.
_
8:
5; 1 3 al x
4
l
lxx
,’
10
/-
5
-
a;.
xe -
XeCi
+ Cl
ii 0’
0
50
200
I50
100 xe
pressure
(TorrJ
Fig. 2. Emission intensity ratio (XeCI*/CI~) the Xe pressure_
as a function of
Fig. 2 summarizes the experimental results on measured fluorescence ratio as a function of Xe pressure. It is clear that the intensity ratio increases linearly with an increase of Xe pressure as expected from eq. (6) and we confirmed it to be independen of Cl, pressures lower than 6 Torr. The curvature observed above 50 Torr Xe pressure exhibits the quenchmg of XeCI* by Xe_ We have measured the fluorescence lifetime of the ‘Zz state of CI?, which was found by a deconvolution method to be 14 i 2 ns at 0.05 Torr Cl,. The pressure is low enough to exclude the probability of removal by collisions and we used this value to calculate the rate constant for the collisional formation of
260
Fig. 3. Emission spectrum of resonant three-photon
358
the E(O&B excitation
Xe*(3P,)
+ Ci, + XeCl* + CI _
(7)
A large collisonal cross section of the excited species is expected from a long-range harpooning mechanism, where the input and exit channels are coupled by an intermediate ion-pair potential curve. It is likely that the reaction surface of the Cl, ‘Zz ion-pair state with Xe might cross with the ion-pair potential (Xe’-Cl,) whose exit channel is XeCl* + Cl just as for reactive quenching of Xe metastable atoms 1201. This assumption is consistent with results of a two-photon assisted reaction of Xe with Cl,, in which Xe and Cl2 might be directly excited to a Teactive channel of the same type as in this study, giving a broad excitation spectrum for the XeCl emission at 308 mn [ 191. With the addition of He, Ar, or Kr, the Cl2 emission bands also decreased in intensity associated with a change of their profde. Fig. 3 is the fluorescence spectrum of an Ar/CIZ mixture excited at 19924.7 cm-l. Under this high-pressure condition, the lZi-lZl fluorescence obviously disappeared. The 258 nm band is now the dominant fluorescence channel, which can be attributed to the E(Oi)-3 %(OS) transition. This result agrees with the previous observations; the E-B
250 Wavelength
photon
14 December 1984
PHYSICS LETTERS
Cl2
: 3.1
Torr
Ar
:
~orr
120
210
230
(nm)
3n(Oz) system observed when the (212 molecules are exited in the presence of AI.
to the lx:
state by a one-
Volume
112, number 4
CHEMICAL
PHYSICS LETTERS
fluorescence could be developed in the electronic dischange and e-beam pumping experiments by admixing unreactive inert gases such as He and Ar to Clj. The E(O> state might be the lowest state among the twenty ion-pan states correlating with Cl-(lS) + Cli+(3P, lD, IS). Collisional interstate transfer terminating on the lowest E(Oi) state obviously completes the deactivation process in the upper ion-pair states. These processes are closely related with the detailed mechanism of Cl, laser at 258 mn.
References
t11 G.W.
King, 1-M. Littlewood and JR. Robins, Chem. Phys. 56 (1981) 145; J.P. Perrot, M. Broyer, J. Chevaleyre and B. Femelt, Chem. Phys. 67 (1982) 59; J. Mol. Spectry. 98 (1983) 161; J.B. Koffend, R. Basis, M. Broyer, J-P. Pique and S. Chummy, Laser Chem. l(1983) 343. f21 J.C.D.Brand,A.R.Hoy,A.K.KalkerandA.B.Yamasbita. J. Mol. Spectry. 95 (1982) 350; J.C.D. Brand and A.R. Hoy, J. Mol. Spectry. 97 (1983) 379. [31 F.W. Dalby, G. Petty-S& M.H.L. Pryce and C. Tai. Can. J. Phys. 55 (1977) 1033; K-K. Lehmann, J. Smolarek and L. Goodman, J. Chem. Phys. 69 (1978) 1569; D.E. Cooper and J-E. Wessel, J. Chem. Phys. 76 (1982) 2155. [4] C. Tai. F-W. Dalby and G.L. Giles. Phys. Rev. 20 (1979) 233. [5] K. Chen. L-E. Steenhoek and E.S. Yeung, Chem. Phys. Letters 59 (1978) 222.
14 December
1984
[6] T. Ishiwata, I. F ulrwara -_ and L Tanaka, Chem. Phys. Letters 89 (1982) 527. [7] T. Ishiwata, I. Fujiwara, T. Shinzawa and T_ Tanaka, J_ Chem. Phys. 79 (1983) 4779. [8] T. Ishiwata and 1. Tanaka, Chem. Phys. Letters 107 (1984) 434. [9] T. Shinzawa, A. TokunaSa, T. Ishiwata, I. Tanaka, K. Kasatani, hi. Kawasaki and H. Sato, J. Chem. Phys. 80 (1984) 5909; T. Isbiwata, H. Ohotoshi and L Tanaka, J. Chem. Phys., to be published. [lo] T. Ishiwata, H. Ohotoshi, M. Sakaki and I. Tanaka, J. Chea Phys. 80 (1984) 1411. [ 1 l] C-H. Chen and M.G. Payne, AppL Phys. Letters 28 (1976) 219; AK. Hoys, Opt. Commun. 28 (1979) 209; hL Diegelmann, K Hohla. F_ Rebentrost and KJKompa, J_ Chem Phyr 76 (1982) 1233. [ 121 MC. Castex, J. Le Calv& D. Haaks, B. Jordan and G. Ziiner, Chem Phyr Letters 70 (1980) 106; Nuovo Cimento B63 (1981) 265. [ 131 M.W. Wilson, R Rothschild and C-K Rhodes, J. Chem. Phys. 78 (1983) 3779. [14] S-D. Peyerimhoff and RJ. Buenker, Chem. Phys. 57 (1981) 279. [ 151 E. Schatzlein, W. Walter, R. Sauerbrey and H. Langhoff, Appl. Phys B27 (1982) 49. [16] J-H. Kolts, J-E. Velazoco and D-W. Setser, J. Chem. Phys. 71 (1979) 1247. [ 171 VS. Dubou, L.E. Gundzenko, L-U. Gurovich and S. Iakovlenko. Chem Phys. Letters 53 (1978) 170; VS. Dubou, V.E. Lapsker, A.N. Samoilova and V-A. Gurvich, Chem. Phyr Letters 83 (1981) 518. [18] B.E. Wilcomb and R. Bumham, J. Chem. Phys. 74 (1981) 6784. [ 191 J-K. Ku, G. Inoue and D-W. Setser, J. Phys. Chem 87 (1983) 2989. [ 201 J-E. Velazazco, J.H. Kolts and D-W_ Setser, J. Chem. Phys. 69 (1978) 4357.
359