J. Phys. Chem. A 2010, 114, 741–744
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Combustion Parametric Optimization for All Gas-Phase Iodine Laser Driven by D2/NF3/DCl Combustion and Self-Pooling of NCl(a) Catalyzed by NF(a)/NF(b) Shukai Tang,* Liping Duo, Fengting Sang, Haijun Yu, Jian Wang, and Yuqi Jin Key Laboratory of Chemical Laser, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ReceiVed: October 12, 2009; ReVised Manuscript ReceiVed: NoVember 13, 2009
Combustion parametric optimization for all gas-phase iodine laser driven by D2/NF3/DCl combustion was performed, and an energy transfer channel called self-pooling of NCl(a) catalyzed by NF(a)/NF(b) was presented. The results show that a flow rate ratio of NF3 and D2 of 0.8 to 1.5 and DCl and D2 of >1.5 is necessary for high efficiency of Cl atoms generation. The results also show that NF(a) and NF(b) from the reaction of HN3 and residual F atoms or from the D2/NF3 combustion have a serious effect on the generation and transport of NCl(a) via the NF(a) direct quenching of NCl(a) or via the catalysis of NF(a)/NF(b) on NCl(a) self-pooling. The generation of NF can be avoided if sufficient DCl was used and the NF3/D2 flow rate ratio was properly controlled. I. Introduction The all gas-phase iodine laser (AGIL)1-8 is a laser device that produces an inversion on the 1315 nm spin orbit transition of atomic iodine via near resonant energy transfer between electronically excited molecule, NCl(a), and ground-state iodine atom.
NCl(a) + I f NCl(X) + I*
(1)
Because NCl(a) can be generated by reactions that occur solely in the gas phase, AGIL is regarded as an attractive potential alternative to chemical oxygen iodine laser (COIL) that uses the energy transfer from electronically excited oxygen, O2(a), to ground-state atomic iodine and suffers the complication from the two-phase chemistry in the production of O2(a).
Cl2 + H2O2 + 2OH- f O2(a) + 2H2O + 2Cl- (2) O2(a) + I f O2(X) + I*
(3)
The successful gain and laser demonstration of AGIL based on reaction of atomic Cl and HN3 have produced NCl(a) via the following reactions
F + DCl f Cl + DF Cl + HN3 f HCl + N3
(4) (5)
Cl + N3 f NCl(a) + N2
(6)
where the F atoms were generated by a DC discharge of F2 and/or NF3 diluted in He. Because the F atom production efficiency of the DC discharge is limited and not suitable for the further development of AGIL, the efforts to use chemical combustor technology to generate F atoms for AGIL have been done.9,10 This article describes the experimental results of generation of NCl(a) using D2/NF3/DCl combustor as a source of Cl atoms. The optimum flow condition for NCl(a) production was obtained. An abnormal branching ratio of NCl(a) and NCl(b) formation suggests that there is an unknown reaction channel * Corresponding author. E-mail:
[email protected] dlp@dicp. ac.cn.
in the generation of NCl(a) and NCl(b). A possible energy transfer channel by which the self-pooling of NCl(a) is quickened with the help of NF(a) and NF(b) catalysis is proposed and discussed. II. Experimental Section A schematic diagram of the experimental setup is shown in Figure 1. The supersonic AGIL device consisted of four major components, including a subsonic D2/NF3/DCl combustor, a converging-diverging nozzle, a series of supersonic HN3 injectors, and a supersonic flow chamber. The combustion chamber converges vertically from 3 to 1 cm and diverges horizontally from 4 to 10 cm and 9 cm deep. Injectors for D2 and NF3/DCl mixture were located on the back wall of the combustion chamber. NF3 and DCl were mixed upstream of the combustor and injected through two rows of 10 holes. D2 was injected through a single row of 10 holes. The combustion process can be described as the following reactions
D2 + NF3 f DF + N2 + F + NF2 + NF + ...
(7)
F + DCl f DF + Cl
(8)
The supersonic nozzle consisted of a 10 cm wide slit with a 0.6 mm throat height and 30° expansion angle. The HN3 injectors were located at the up and down walls of the supersonic nozzle exit plane and consisted of two rows of 38 holes, each 0.5 mm in diameter. The supersonic flow chamber begins at the nozzle exit plane and extends downstream to the end of the reactor, with a vertical height of 1.0 cm and 4° expansion angle. All reagent flow rates were controlled by gas-pressure regulators and calibrated sonic orifices. The flow rate of HN3 was calculated with the pressure of the entrance of HN3 injector and the total throat area of HN3 injectors. HN3 was synthesized by the reaction of NaN3 and oleic acid (C17H33COOH)11 and stored in a 1000 L tank. For safety, the partial pressure of HN3 was kept 1.5 is necessary for high efficiency of Cl atom generation. Figure 5 also shows that a small amount of NF(a) and NF(b) existed in the supersonic flow, although DCl was sufficient for the replacement of F atoms. NF(a) and NF(b) were not produced through the reaction of F atoms and HN3 and possibly generated in the combustor just as described in the reaction 7. The supposition of NF(a) and NF(b) produced in the combustor was proven through observing the spectrum of NF(a) and NF(b) in the supersonic
flow in the absence of HN3. The spectrum collection results not only prove that NF(a) and NF(b) can be generated in the D2/NF3 combustion but also show that NF(a) and NF(b) production can be enhanced along with the increasing flow rate ratio of NF3 and D2. The most interesting thing was that the branching ratio of NCl(a) and NCl(b) formation was not fixed in the presence of NF(a) and NF(b), as shown in Figures 4 and 5. According to the reactions of Cl and HN3 to produce NCl(a) and NCl(b) above-mentioned, the branching ratio of NCl(a) and NCl(b) formation should be constant; however, Figures 4 and 5 show that NCl(b) emission intensity increased remarkably, whereas NCl(a) emission intensity decreased in the presence of NF(a) and NF(b). The abnormal branching ratio of NCl(a) and NCl(b) formation indicated that there was an unknown channel of energy transfer between NCl(a) and NCl(b). According to experimental data presented in Figures 4 and 5, confirmation experiments for NF(a) and NF(b) formation in D2/NF3/DCl combustor and the energy level of NCl and NF (Figure 6), an energy transfer channel called self-pooling of NCl(a) catalyzed by NF(a) and NF(b) was presented as the following reactions and illustrated in Figure 7.
NCl(a) + NF(a) f NF(b) + NCl(X)
∆E ≈ 0.22 ev (15)
NCl(a) + NF(b) f NF(a) + NCl(b)
∆E ≈ 0.21 ev (16)
The bimolecular direct energy pooling of NCl(a) was described as the follows16-19
2NCl(a) f NCl(X) + NCl(b)
∆E ≈ 0.43 ev (17)
Reaction 15 was an important channel in the interaction between NF and NCl,20-22 but reaction 16 has not attracted attention. We think that electronically excited NF molecules, NF(a) and NF(b), play an important role just as a catalyzer that reduces the energy barrier and quicken bimolecular energy pooling or self-quenching of NCl(a). The role of NF(a) and NF(b) is similar to that of I(2P3/2) and I(2P1/2) in the NCl(a) self-pooling.23 When the particle number density of NCl(a) is smaller than that of NF(a), the energy transfer channel of reaction 15 is
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J. Phys. Chem. A, Vol. 114, No. 2, 2010
dominant, and the particle number density of NF(b) increases markedly, whereas fewer NCl(b) molecules are produced via reactions 16 and 17, this mechanism can explain that NCl(b) emission intensity did not increase remarkably, just as shown in Figure 4 and mentioned in reference 21. The cooperation of NF(a) and NF(b) on the energy transfer from NCl(a) to NCl(b) will be enhanced if the density of NF(a) or NF(b) is much smaller than that of NCl(a), the energy transfer channel of selfpooling of NCl(a) with the help of catalysis of NF(a) and NF(b) will be dominant, and NCl(b) emission will increase markedly, just as described in Figure 5. There is an optimum flow rate ratio of NF3 and D2 for the generation of F atom; consequently, for Cl atom production, the density of F atom decreases when the flow rate ratio of NF3 and D2 is to some extent in excess. In Figure 5, NCl(b) emission was enhanced via reactions 15 and 16 when the NF3 flow rate was 22 mmol/s, mainly because of the Cl atom density decrease. On one hand, the direct NF(a) quenching of NCl(a) and the catalysis of NF(a) and NF(b) on the bimolecular energy pooling of NCl(a) are a great disadvantage to the generation and transport of NCl(a). On the other hand, NF is a very strong quencher of electronically excited atomic iodine, I(2P1/2).23,24 To avoid NF formation in AGIL-based D2/NF3/DCl combustion, sufficient DCl should be added to the combustor to exhaust F atoms completely, and a proper flow rate ratio of NF3 and D2 should be controlled to avoid NF(a) and NF(b) direct formation in the combustor, as shown in Figure 5. IV. Conclusions The combustion parametric optimization for all gas-phase iodine laser driven by D2/NF3/DCl combustion has been done. The results show that a flow rate ratio of NF3 and D2 of 0.8 to 1.5 and DCl and D2 of >1.5 is suitable for high efficient atomic Cl generation. The results also show that residual F atom has a bad effect on the NCl(a) generation and transports mainly duo to the reaction of F atoms and HN3 to produce NF(a), which is a strong quencher of NC(a) via the direct NF(a) quenching of NCl(a) and the catalysis of NF(a) and NCl(b) on bimolecular self-pooling of NCl(a). A small quantity of NF(a) and NF(b) can be produced in the D2/NF3/DCl combustor if the NF3/D2 flow rate ratio cannot be properly controlled, which also has a
Tang et al. bad effect on the NCl(a) production and transport mainly via the catalysis of NF(a) and NF(b) on the bimolecular NCl(a) self-pooling. Therefore, the DCl should be sufficient for the complete replacement of F atoms, and the flow rate ratio of NF3 and D2 should be properly controlled to get a higher efficiency of NCl(a) generation. References and Notes (1) Yang, T. T.; Bower, R. D. Proc. SPIE 1990, 1225, 159. (2) Ray, A. J.; Coomber, R. D. J. Phys. Chem. 1995, 99, 7849. (3) Herbelin, J. M.; Henshaw, T. L.; Brent, D. R.; Anderson, B. T.; Tate, R. F.; Madden, T. J.; Manke, G. C., II; Hager, G. D. Chem. Phys. Lett. 1999, 299, 583. (4) Henshaw, T. L.; Manke, G. C., Jr.; Madden, T. J.; Berman, M. R.; Hager, G. D. Chem. Phys. Lett. 2000, 325, 537. (5) Manke, G. C., II; Cooper, C. B.; Dass, S. C.; Madden, T. J.; Hager, G. D. IEEE J. Quantum Electron. 2003, 39, 995. (6) McDermott, W.; Coombe, R.; Gilbert, J.; Lambert, Z.; Heldt, M. Proc. SPIE 2004, 5334, 11. (7) Masuda, T.; Nakamura, T.; Endo, M.; Uchiyama, T. Proc. SPIE 2008, 7131, 713108. (8) Masuda, T.; Nakamura, T.; Endo, M.; Uchiyama, T. Chem. Phys. Lett. 2009, 476, 25. (9) Manke, G. C., II; Madden, T. J.; Cooper, C. B.; Hager, G. D. Proc. SPIE 2005, 5792, 97. (10) Tang, S. K.; Duo, L. P.; Yu, H. J.; Wang, J.; Sang, F. T.; Jin, Y. Q. Chin. J. Lasers (Chin. Ed.) 2009, 36, 1403. (11) Tang, S. K.; Duo, L. P.; Jin, Y. Q.; Yu, H. J.; Wang, J.; Sang, F. T. Proc. SPIE 2007, 6346. (12) Liu, X.; MacDonald, M. A.; Coombe, R. D. J. Phys. Chem. 1992, 96, 4907. (13) Manke, G. C., II; Henshaw, T. L.; Madden, T. J.; Hager, G. D. Chem. Phys. Lett. 1999, 310, 111. (14) Habdas, J.; Wategaonkar, S.; Seter, D. W. J. Phys. Chem. 1987, 91, 452. (15) Du, K. Y.; Seter, D. W. J. Phys. Chem. 1990, 94, 2425. (16) Manke II, G. C.; Seter, D. W. J. Phys. Chem. A 1998, 102, 7257. (17) Henshaw, T. L.; Herrera, S. D.; Haggquist, G. W.; Schlie, L. A. J. Phys. Chem. A 1997, 101, 4048. (18) Komissarov, A. V.; Manke, G. C., II; Davis, S. J.; Heaven, M. C. J. Phys. Chem. A 2002, 106, 8427. (19) Tschumper, G. S.; Heaven, M. C.; Morokuma, K. J. Phys. Chem. A 2002, 106, 8453. (20) Benard, D. J.; Chowdhury, B. K.; Seder, T. A.; Michels, H. H. J. Phys. Chem. 1990, 94, 7507. (21) Exton, D. B.; Gilbert, J. V.; Coombe, R. D. J. Phys. Chem. 1991, 95, 7758. (22) Heweett, K. B.; Manke, G. C., II; Seter, D. W.; Brewood, G. J. Phys. Chem. A 2000, 104, 539. (23) Yang, T. T. Proc. SPIE 1994, 2119, 122. (24) Benard, D. J. J. Phys. Chem. 1996, 100, 8316.
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