ISSN:
1434-6079
Keywords:
PACS. 33.20.Ni Vacuum ultraviolet spectra – 33.80.Gj Diffuse spectra; predissociation, photodissociation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract: Rotationally resolved spectral lines in the C - X (1, 0) band of carbon monoxide are investigated under high resolution using a coherent vacuum ultraviolet laser source, continuously tunable near 107 nm. Transition frequencies are determined by calibrating against a reference standard of iodine lines, recorded with saturation spectroscopy in the visible range, yielding an absolute accuracy of 0.003 cm-1 in the vacuum ultraviolet. Improved molecular constants for the excited state are derived and no effects of perturbation are found at the present level of accuracy. Line broadening measurements result in information on the excited state lifetime of the C 1 Σ + , v = 1 state for five natural isotopomers of carbon monoxide: τ( 12 C 17 O ) = 280 ps, τ( 12 C 18 O ) = 210 ps, τ( 13 C 16 O ) = 295 ps, τ( 13 C 17 O ) = 160 ps, and τ( 13 C 18 O ) = 150 ps. Within the accuracy of the present measurements no effects of J-dependent lifetimes were observed, for neither of the isotopomers. In addition direct time domain measurements of the lifetime of the C 1 Σ + , v = 0 and v = 1 states of the main isotopomer are performed in a pump-probe experiment using a picosecond VUV-laser, yielding τ( 12 C 16 O ) = 1780 ps for v = 0 and τ( 12 C 16 O ) = 625 ps for v = 1. For C 1 Σ + , v = 0 in 12C16O and 13C16O the same lifetime is found; this lifetime matches experimental values of the oscillator strength and hence supports previous results showing pure radiative decay in this state; the error margins however do not exclude some low level of predissociation. The measurements indicate that the C 1 Σ + , v = 0 state of the 13C18O isotopomer is predissociated with an estimated yield of 17% (i.e. above the level of predissociation for 12C16O.) From the combined data predissociation yields upon excitation of the C 1 Σ + , v = 1 state are derived, lying in the range 0.84-0.91 for the five less abundant isotopomers; for the main 12C16O isotopomer a strongly deviating predissociation yield of 0.65 is deduced.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s100530170182
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