Premium
Photodynamics of Small Aliphatic Ketones in a Supersonic Jet Expansion
Author(s) -
Haas Yehuda,
Zuckermann Hanna
Publication year - 1989
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198900051
Subject(s) - chemistry , intersystem crossing , supersonic speed , van der waals force , dissociation (chemistry) , atomic physics , photochemistry , molecule , ground state , chemical physics , absorption spectroscopy , molecular physics , excited state , thermodynamics , optics , physics , organic chemistry , singlet state
The photodynamics of acetone and some other simple aliphatic ketones in the nπ* state are discussed in the light of recent results obtained in seeded supersonic beams. The Born‐Oppenheimer approximation is used to describe the sequence of events beginning with light absorption and ending in molecular fragmentation. Intersystem crossing is shown to be an important process even for the isolated molecule. Its rate increases with the internal energy and may be related to the density of states in the triplet state. For all molecules studied so far, the results can be rationalized by assuming that dissociation takes place on the triplet surface, the S 1 surface being stable in the energy range pertinent to these experiments (up to 35,000 cm −1 above the ground state). Fluorescence spectroscopy may be used also to detect small clusters. In the case of acetone, their presence is indicated by the decrease in the intensity of some spectral lines as a function of cooling efficiency. The results are used to estimate an upper limit for the van der Waals binding energies.