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Laser fluorescence excitation spectra and dispersed fluorescence spectra of jet‐cooled 3‐, 4‐, and 5‐isopropyltropolone in the S1–S0 region have been measured to investigate the effect of unsymmetrical and symmetrical substitution of an isopropyl group on proton tunneling. The 0++ and 0−+ transitions have been identified in the excitation spectra of 3‐isopropyltropolone and its −OD derivative. The tunneling doublet splittings in the S1 state have been determined to be 58 and 14 cm−1 for normal and deuterated species, respectively. The increase in tunneling splitting of 3‐isopropyltropolone compared with that of tropolone suggests that the substitution of the isopropyl group induces an asymmetry in the double‐minimum potential well. In contrast with the excitation spectrum of 3‐isopropyltropolone, no 0−− and 0−+ transitions have been detected in 4‐ and 5‐isopropyltropolone. The nonobservation of these transitions is likely to be due to substantial increase in the potential‐energy barrier to tunneling in th...

Organic residues which remain on printed wiring boards (PWBs) even after washing with chlorofluorocarbon substitutes are excited optically and their quantities are estimated with significant accuracy on the basis of their fluorescence. The thickness of residues is related linearly to the intensity of their fluorescence and can be estimated even for very thin layers. The distribution of residues on PWBs is visualized as a two-dimensional map of fluorescence intensity, in which variations in intensity are represented as variations in color. This proposed estimation method is applied here to an examination of the relationship between flux residues and electromigration on PWBs, as well as to an estimation of the effectiveness of washing with trichloroethane substitutes.

Laser excited fluorescence spectra and dispersed fluorescence spectra of 3-isopropyltropolone have been measured in ultracold gas phase by a supersonic expansion. The tunneling splittings in the zero-point level of the S1 state have been determined to be 58 and 14 cm−1 for normal and deuterated species, respectively.