Temperature-dependent study of the kinetics of Ta(a⁴F_3/2) with O₂, N₂O, CO₂ and NO

Abstract

The gas-phase reactivity of Ta(a⁴F_3/2) with O₂, N₂O, CO₂ and NO in the temperature range 296–548 K is reported. The room-temperature removal rate constants for the spin–orbit excited states (a⁴F_J, J=5/2, 7/2, 9/2) are reported for these oxidants and CH₄. Tantalum atoms were produced by the photodissociation of tetracarbonyl cyclopentadienyl tantalum(0) [Ta(C₅H₅)(CO)₄] and detected by laser-induced fluorescence. The reaction rate constants of the a⁴F_3/2 ground state with O₂, N₂O, CO₂ and NO are temperature dependent. The disappearance rates in the presence of all the reactants are independent of total pressure, indicating a bimolecular abstraction mechanism. The bimolecular rate constants are described in Arrhenius form by k(O₂)=(1.7±0.2) ×10^-10 exp(-7.8±0.4 kJ mol^-1/RT) cm³ s^-1, k(N₂O)=(7.1±1.0)×10^-11 exp(-13.6±0.6 kJ mol^-1/RT) cm³ s^-1, k(CO₂)=(1.0±0.1)×10^-10 exp(-26.8±0.5 kJ mol^-1/RT) cm³ s^-1 and k(NO)=(1.0±0.2)×10^-10 exp(-1.6±0.8 kJ mol^-1/RT) cm³ s^-1 where the uncertainties are ±2σ. The removal rates of the spin–orbit excited states with O₂, N₂O, CO₂ and NO are spin–orbit state dependent and are generally faster than for the ground state. The a⁴F_3/2 ground state is unreactive with methane, although the spin–orbit excited states are quenched by methane. The a⁴F_5/2, a⁴F_7/2 and a⁴F_9/2 states have second-order room-temperature removal rate constants in methane of 6.0×10^-13, 9.5×10^-13 and 2.3×10^-11 cm³ s^-1, respectively.

References

1. (a) D. Ritter and J. C. Weisshaar, J. Am. Chem. Soc., 1990, 112, 6425; (b) D. Ritter, J. J. Carroll and J. C. Weisshaar, J. Phys. Chem., 1992, 96, 10636; (c) J. J. Carroll and J. C. Weisshaar, J. Am. Chem. Soc., 1993, 115, 800; (d) J. J. Carroll, K. L. Haug and J. C. Weisshaar, J. Am. Chem. Soc., 1993, 115, 6962; (e) J. J. Carroll, K. L. Haug, J. C. Weisshaar, M. R. A. Blomberg, P. E. M. Siegbahn and M. Svensson, J. Phys. Chem., 1995, 99, 13955; (f) J. J. Carroll, J. C. Weisshaar, P. E. M. Siegbahn, C. A. M. Wittborn and M. R. A. Blomberg, J. Phys. Chem., 1995, 99, 14388; (g) J. J. Carroll and J. C. Weisshaar, J. Phys. Chem., 1996, 100, 12355.
2. (a) M. A. Blitz, S. A. Mitchell and P. A. Hackett, J. Phys. Chem., 1991, 95, 8719; (b) C. E. Brown, S. A. Mitchell and P. A. Hackett, Chem. Phys. Lett., 1992, 191, 175; (c) L. Lian, S. A. Mitchell and D. M. Rayner, J. Phys. Chem., 1994, 98, 11637; (d) J. M. Parnis, R. D. Lafleur and D. M. Rayner, J. Phys. Chem., 1995, 99, 673.
3. K. Senba, R. Matsui and K. Honma, J. Phys. Chem., 1995, 99, 13992.
4. M. L. Campbell and R. E. McClean, J. Chem. Soc., Faraday Trans., 1995, 91, 3787.
5. M. L. Campbell, R. E. McClean and J. S. S. Harter, Chem. Phys. Lett., 1995, 235, 497.
6. JANAF Thermochemical Tables, J. Phys. Chem. Ref. Data, 1985, 14, Suppl. 1.
7. C. E. Moore, Atomic Energy Levels as Derived from the Analysis of Optical Spectra, Natl. Stand. Ref. Data Ser. (US National Bureau of Standards) 1971, NSRDS-NBS 35.
8. E. A. Den Hartog, D. W. Duquette and J. E. Lawler, J. Opt. Soc. Am. B, 1987, 4, 48.
9. R. L. Jackson, J. Chem. Phys., 1990, 92, 807.
10. J. M. Parnis, R. D. Lafleur and D. M. Rayner, J. Phys. Chem., 1995, 99, 673.
11. M. L. Campbell, J. Phys. Chem., 1996, 100, 19430.
12. R. E. McClean and L. Pasternack, J. Phys. Chem., 1992, 96, 9828.
13. M. L. Campbell and R. E. McClean, J. Phys. Chem., 1993, 97, 7942.
14. C. W. Bauschlicher Jr. and S. R. Langhoff, J. Chem. Phys., 1986, 85, 5936.
15. J. M. Sennesal and J. Schamps, Chem. Phys., 1987, 114, 37.
16. C. J. Nelin and C. W. Bauschlicher Jr., Chem. Phys. Lett., 1985, 118, 221.
17. M. Krauss and W. J. Stevens, J. Chem. Phys., 1985, 82, 5584.
18. W. Weltner Jr. and D. McLeod Jr., J. Chem. Phys., 1965, 42, 882.
19. J. M. Dyke, A. M. Ellis, M. Fehér, A. Morris, A. J. Paul and J. C. H. Stevens, J. Chem. Soc., Faraday Trans., 1987, 83, 1555.
20. R. E. McClean, M. L. Campbell and E. J. Kölsch, J. Phys. Chem. A, 1997, 101, 3348.
21. C. E. Brown, S. A. Mitchell and P. A. Hackett, J. Phys. Chem., 1991, 95, 1062.
22. D. E. Clemmer, K. Honma and I. Koyano, J. Phys. Chem., 1993, 97, 11480.
23. D. Ritter and J. C. Weisshaar, J. Phys. Chem., 1989, 93, 1576.
24. (a) P. M. Futerko and A. Fontijn, J. Chem. Phys., 1991, 95, 8065; (b) P. M. Futerko and A. Fontijn, J. Chem. Phys., 1992, 97, 3861; (c) P. M. Futerko and A. Fontijn, J. Chem. Phys., 1993, 98, 7004; (d) D. P. Belyung, P. M. Futerko and A. Fontijn, J. Chem. Phys., 1995, 102, 155.
25. M. L. Campbell, J. Chem. Soc., Faraday Trans., 1996, 92, 4377.
26. M. L. Campbell and J. R. Metzger, Chem. Phys. Lett., 1996, 253, 158.
27. M. L. Campbell, J. Chem. Phys., 1996, 104, 7515.
28. R. E. McClean, M. L. Campbell and R. H. Goodwin, J. Phys. Chem., 1996, 100, 7502.
29. M. L. Campbell, K. L. Hooper and E. J. Kölsch, Chem. Phys. Lett., in press.
30. (a) U. S. Akhmadov, I. S. Zaslonko and V. N. Smirnov, Kinet. Catal., 1988, 29, 251; (b) U. S. Akhmadov, I. S. Zaslonko and V. N. Smirnov, Kinet. Catal., 1988, 29, 808.
31. J. M. Parnis, S. A. Mitchell and P. A. Hackett, J. Phys. Chem., 1990, 94, 8152.
32. S. A. Mitchell and P. A. Hackett, J. Chem. Phys., 1990, 93, 7822.
33. R. Matsui, K. Senbar and K. Honma, J. Phys. Chem. A, 1997, 101, 179.
34. R. E. McClean and M. L. Campbell, in preparation.
35. J. S. S. Harter, M. L. Campbell and R. E. McClean, Int. J. Chem. Kinet., 1997, 27, 367.
36. P. J. Dagdigian and M. L. Campbell, Chem. Rev., 1987, 87, 1.