Abstract
A new technique, double absorption photofragment spectroscopy (DAPS), has been developed in order to follow the time evolution of unimolecular processes in isolated molecules. Molecules removed from collisions in a molecular beam are prepared in well defined initial states by an initiation laser pulse As this state distribution evolves, it is monitored as a function of time by a second, delayed, probe laser pulse which, by exciting the molecules to a higher dissociative state, forces them to emit information-carrying particles. These particles, molecular fragments from photodissociation, are detected by photofragment spectroscopy, which can be used to derive information about the time evolution of the unimolecular process by following changes in such parameters as population, angular distribution, fragmentation pattern, and energy partitioning. As an initial demonstration of this technique, the predissociation of the iodine B state has been studied. The lifetime for the B state was found to vary between 770 and 1600 nsec depending on the v′ J′ population distribution prepared by the initiation laser pulse. In addition, the characterization of a state, invisible in the ordinary absorption spectrum because transition to it is parity forbidden, is illustrated through the sequential absorption of two photons.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
Similar content being viewed by others
References
J. Jortner, S. A. Rice, and R. M. Hochstrasser, Advan. Photochem. 7, 149 (1969); E. W. Schlag, S. Schneider, and S. F. Fischer, Ann. Rev. Phys. Chem. 22, 465 (1971); V. Lawetz, G. Orlandi, and W. Siebrand, J. Chem. Phys. 56, 4058 (1972).
Other experiments which have used two laser pulses to excite an emitting state include: W. C. Lineberger and T. A. Patterson, Chem. Phys. Lett. 13, 40 (1972); V. S. Letokhov, Science 180, 451 (1973); C. B. Moore, Accounts Cheml. Resh. 6, 323 (1973).
A description of the apparatus is found in G. E. Busch, J. F. Cornelius, R. T. Mahoney, R. I. Morse, D. W. Schlosser, and K. R. Wilson, Rev. Sci. Instr. 41, 1066 (1970). Specific molecules which we have studied include a) C12 and Br2: K. R. Wilson, in Symposium on Excited State Chemistry, edited by J. N. Pitts, Jr. (Gordon and Breach, New York, 1970); b) I2: R. J. Oldman, R. K. Sander, and K. R. Wilson, J. Chem. Phys. 54, 4127 (1971); c) NO2: G. E. Busch and K. R. Wilson, J. Chem. Phys. 56, 3626 and 3638 (1972); d) NOC1: G. E. Busch and K. R. Wilson, J. Chem. Phys. 56, 3655 (1972); e) alkyl iodides: S. J. Riley and K. R. Wilson, J. Chem. Soc. Faraday Disc. 53, 132 (1972); f) ICN: G. Hancock and K. R. Wilson, in Fundamental and Applied Laser Physics: Proceedings of the Esfahan Symposium August 29-September 5, 1971, edited by M. S. Feld, A. Javan, and N. Kurnit (John Wiley and Sons, New York, 1973); g) acetone: G. Hancock and K. R. Wilson, Proceedings of the Fourth International Symposium on Molecular Beams, Cannes, France, July, 1973.
The Nd oscillator-amplifier system was designed and built under contract by Wilhelm Hagen at American Optical Co.
K. R. Wilson, Bull. Am. Phys. Soc. 18, 30 (1973).
R. S. Mulliken, J. Chem. Phys. 55, 288 (1971).
J. Tellinghuisen, J. Chem. Phys. 57, 2397 (1972).
J. Tellinghuisen, J. Chem. Phys. 58, 2821 (1973).
E. Wasserman, W. E. Falconer, and W. A. Yager, Berh. Bunsenges. physik. Chem. 72, 248 (1968).
A. Chutjian and T. C. James, J. Chem. Phys. 51, 1242 (1969).
D. G. Youmans, L. A. Hackel, and S. Ezekiel, J. Appl. Phys. 44, 2319 (1973).
K. C. Shotton and G. D. Chapman, J. Chem. Phys. 56, 1012 (1972).
G. A. Capelle and H. P. Broida, J. Chem. Phys. 58, 4212 (1973).
G. E. Busch, R. T. Mahoney, R. I. Morse, and K. R. Wilson, J. Chem. Phys. 51, 837 (1969).
G. Herzberg, Spectra of Diatomic Molecules (D. Van Nostrand Company, Inc., Princeton, New Jersey, 1950).
G. D. Chapman and P. R. Bunker, J. Chem. Phys. 57, 2951 (1972); M. S. Child, J. Mol. Spectry. 45, 293 (1973).
T. R. Bader and A. Gold, Phys. Rev. 171, 997 (1968); C. Jonah, J. Chem. Phys. 55, 1915 (1971); and R. N. Zare, Mol. Photochem. 4, 1 (1972).
R. K. Sander and K. R. Wilson, to be published.
R. D. Clear and K. R. Wilson, J. Mol. Spectry. 47, 39 (1973).
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1974 Plenum Press, New York
About this chapter
Cite this chapter
Riley, S.J., Sander, R.K., Wilson, K.R. (1974). Time Evolution of Unimolecular Processes in Isolated Molecules by Crossed Laser and Molecular Beams. In: Brewer, R.G., Mooradian, A. (eds) Laser Spectroscopy. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-4517-6_43
Download citation
DOI: https://doi.org/10.1007/978-1-4613-4517-6_43
Publisher Name: Springer, Boston, MA
Print ISBN: 978-1-4613-4519-0
Online ISBN: 978-1-4613-4517-6
eBook Packages: Springer Book Archive