Laser desorption followed by jet-cooling allows wavelength-selective as well as massselective detection of molecules desorbed from a surface without fragmentation. The cooling characteristics and detection sensitivity of laser desorption jet-cooling of organic molecules are investigated. From the rotational contour of the electronic origin of the $1 ~-So transition of laserdesorbed anthracene, rotational cooling to 5-10 K is demonstrated. Vibrational cooling is studied for laser-desorbed diphenylamine, a molecule with low-energy vibrations, and a vibrational temperature below 15 K is found. The absolute detection sensitivity is determined for the perylene molecule. Using two-color (1 + 1) resonance enhanced multi-photon ionization (with a measured ionization efficiency of 0.25) for detection, it is found that one ion is produced in the detection region for every 2 x 105 perylene molecules evaporated from the desorption laser spot. A two-color (1 + I) REMPI spectrum (400 points) of perylene is recorded using only 30 picogram of material.

No abstract

No abstract

Gas phase absorption spectra have been measured for one primary, three secondary, and two tertiary alkyl radicals in the 195 to 370 nm wavelength range. Radicals were generated by Hg-photosensitized reactions and observed by modulation spectroscopy. The pattern of bands observed agrees well with ab initio predictions for the 3s, 3p, and 3d Rydberg transitions and can be reproduced by a Rydberg formula using experimental vertical ionization potentials and normal quantum defects. Oscillator strengths and condensed phase blue shifts are consistent with the Rydberg assignment. A similarity with the spectra of primary, secondary, and tertiary amines is noted.

The following full text is a publisher's version.For additional information about this publication click this link. http://hdl.handle.net/2066/99056Please be advised that this information was generated on 2024-05-29 and may be subject to change.