The rotational spectrum of 2-indanone

The rotational spectrum of 2-indanone has been analysed in the 26.5-40 GHz frequency region. The ground state, the first five excited states of the five-membered ring bending mode and the first excited state of the ring twisting and butterfly modes have been assigned and analysed. From the ground state inertial defect and the variation of the rotational parameters with the ring bending quantum number a strictly planar C2v equilibrium conformation has been established. A one-dimensional potential function of the quadratic-quartic type V(X) = 3.3(7) (X4 + 11.66(15)X2)cm-1 has been derived for the bending vibration.