ISSN:
1434-6079
Keywords:
36.40
;
33.20E
;
33.80G
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The narrow lines on top of the broad homogeneous background of the (C2H4)2 predissociation spectrum are studied. The high resolution spectra are measured tuning the length of a CO2 waveguide laser by means of a PZT yielding a frequency scan of 230 MHz around the CO2 laser lines. In the absense of power broadening a minimum non-instrumental linewidth of 3.5 MHz fwhm is found, corresponding to a lower limit for the predissociation lifetime of 45 ns. From the power broadening of the strongest sharp line a transition dipole moment of 0.14 Debye has been determined. To this transition corresponds a saturation fluenceF sat=3 µJ/cm2, in strong contrast withF sat=20 mJ/cm2 for the broad background. The dependence of the ratio structure/background on the concentration of C2H4 in He, on the source temperature and on the stagnation pressure, yields insight in the origin of the co-existence of the broad background and the narrow lines. Evidence is found that the sharp lines are due to dimers with low internal energies, whereas the background originates mainly from dimers with higher internal energy. By means of a two-laser experiment it is shown that the sharp peaks are inhomogeneous. Moreover, the first laser can significantly diminish the background predissociation signal produced by the second laser without consequences for the height of the sharp peaks.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01384606
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