The Stark effect on the rotational lines of the 1+–0 band of the 3A2–1A1 (π* ← n) transition of formaldehyde has been studied using field strengths up to 25 kV/cm. Measurements of the Stark splittings and shifts for the Q3(3, 3), R2(3, 3), Q2(3, 3), and Q2(5, 5) lines in parallel polarization lead to a value of 1.29 ± 0.03 D for the dipole moment of formaldehyde in its 3A2-excited state. This value is significantly smaller than the value (μ′ = 1.56 ± 0.07 D) obtained by Freeman and Klemperer for the corresponding 1A2-excited state. A few measurements on lines of the 0+–0 band of the 3A2–1A1 system show that the Stark splittings and shifts are closely similar (± 3%) to those for the 1+–0 band.The spin constants for the 3A2 state have been redetermined and are:[Formula: see text]The Stark splittings show conclusively that the line assigned in earlier work as R1(3, 3) is indeed a Q2(3, 3) line in agreement with the intensity formulas of Hougen.

The bands of the 3500 Ǻ transition of azulene-do and azulene-ds show two unequal peaks 2.3 cm-l apart, followed by closely spaced fine structure. These bands have been analysed as type A bands of a planar, prolate asymmetric top. Rotational constants for both molecules in the excited state have been determined. The fine structure is due to multiple line coincidences in the high-J, low-K region of the qP branch. To each multiple line can be attributed a running number n = J+m, where m = J-K-1. Given sufficient resolving power, such "lines" should be rather commonly observed in type A and type B bands of large, planar, prolate molecules.

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The 2800 Å forbidden 1 Σ u r 1 Σ g + transition of dicyanoacetylene shows conventional vibronic origins due to the two π g vibrations and a third involving the lower π u vibration. For the latter we argue against a magnetic dipole mechanism and propose that the intensity is electric dipole, involving coupling to a π* r n state of reduced point symmetry (C ∞V or less). The strongest band in the spectrum may be another such origin, but there is a competing assignment and neither meets expectations of intensities in related bands. While the vibrational structure is emphatic that the excited-state remains linear, the rotational constants extracted from the principal bands, all double-headed and violet-degraded (∆B 0 positive), present problems. The apparent contraction or bending of the molecule thus indicated can be countered by large corrections that yield negative values of the equilibrium constant ∆B e . The size of these corrections and further B values extracted from sequence bands indicate that rotational constants are not uniformly linear in the quantum numbers of the bending vibrations. † Part of the special issue "Charles S. Parmenter Festschrift".