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Six bands have been observed in the magnetic rotation spectrum of acrolein at 4040, 4069, 4122, 4178, 4220, and 4322 Å. The first five bands are assigned to the 3A″–1A′ (π*–n) transition of trans acrolein with the 0–0 band at 4122 Å. The sixth band at 4322 Å is assigned as the 0–0 band of the 3A″–1A′ (π*–n) transition of the cis (or gauche) isomer. The 3A″ state of the cis (or gauche) isomer lies below the corresponding state of the trans isomer by a similar interval to that found earlier for the 1A″ (π*–n) states. The reverse situation exists for the ground states.The absorption spectrum has also been reinvestigated using up to 30 m atm of gas in a cell heated to 180 °C. New assignments are given for some of the bands.

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The ozone ultraviolet spectrum has been re-examined at low temperature to clarify features of photochemical interest. The origin of the system is a diffuse band at 28 450 cm−1, the long wavelength limit of band structure in the cold spectrum. The bands toward higher frequencies are identified as sequences of the upper state bending (333 cm−1) and symmetrical stretching (600 cm−1) modes. This band structure converges to a limit near 32 400 cm−1, consistent with the energy required to form O(1D) plus O2(1Δ). Both the shading of the bands and sequences which appear suggest that the Huggins bands are that part of the Hartley-Huggins system which lies below the dissociation limit, the system being a single transition 1B2← X 1A1. The component of the continuum due to excitation of the ν010″ bending mode is shown to be similar to that arising from the ν000″ ground state, except for a shift toward lower energy equal to the vibrational excitation energy. A rationale for predicting the effect of temperature on the shape of the continuum is presented.