Knowledge Bank

Several lower vibronic bands of the $A¯A\prime (S1)\leftarrow X¯A\prime \prime (S0)$ have been recorded under molecular beam conditions with a pulsed amplified ring laser. The rotational temperature of the coldest spectra are estimated to be 0.7K. The spectra contain well resolved lines which can be assigned to transitions between both the a-a and e-e torsional levels. Spectra were also recorded at a higher rotational temperature. These spectra consist predominantly of transitions between a-a torsional levels. The results of our rigid-rotor analysis of the spectra of the lower vibronic bands of acetaldehyde will be presented. Emphasis has been placed on obtaining reliable estimates of the band origins of these bands. The origin frequencies are then used to test the quality of a concurrent ab-initio calculation performed by Moule, Nino and Munoz-Caro.