Photodissociation and Spectroscopy of Carbon Monoxide
The tunable and narrowband XUV-laser is used in our laboratory for the study of high-lying predissociating states of carbon monoxide and its isotopomers. The detection technique employed is 1 XUV + 1 UV two-photon ionization.
The intensities in such a photoionization process is a very sensitive tool for the determination of relative lifetimes. The competition between dissociative decay and forced ionization by the UV laser field is a delicate handle to derive rather slow predissociation channels. In particular it is suitable to find information on so-called accidental predissocation phenomena. Absolute values of predissociative lifetimes can be derived from linewidth measurements; due to our small source bandwidth of 0.3 cm-1 of the XUV-laser a determination of lifetimes is well feasible.
With the help of time-of-flight mass separation spectra of different isotopes can be studied in simultaneous scans. Up to present we have been limited to the wavelength domain 90.5-108 nm in our experiments. Our goal is to extend this range.
We are investigating states in the energy range corresponding to 90.5-91.5 nm. Also we are comparing spectra recorded with our XUV laser with spectra recorded with a synchrotron source at the Photon Factory, which is part of the KEK-Facility in Tsukuba, Japan.
Recently a pulsed-dye-amplifier (PDA)-laser was installed producing nearly Fourier-transform limited pulses (at 5 ns). After nonlinear upconversion to the third harmonic radiation XUV radiation of a bandwidth as narrow as 250 MHz could be generated, which is used for determining lifetimes and for precision spectroscopy of CO.
The figure demonstrates a typical result obatined with this PDA-laser system:
From the linewidth we obtain a value for the lifetime of the f-parity levels of the L-1-Pi (4p-pi) Rydberg state of CO: 1.0 +/- 0.3 ns. Moreover the absolute frequency is determined from a relative calibration with respect to the I2-line measured in saturated absorption.
See the list of publications of our group for more information on this topic.
In the project on the Photodissociation and Spectroscopy of CO we collaborate with:
Dr. K.P. Huber of the National Research Council of Canada
Dr. P. Cacciani of Laboratoire Aime Cotton, Orsay, France
Dr. C.-G. Wahlstrom, prof. A. L'Huiller and C. Lynga of the Lund Laser Centre