Laser-rf double-resonance study of SiO⁺

Abstract

We used the laser-rf double resonance method to measure 15 fine structure intervals for rotational quantum numbers ranging from N = 5 to 79 of the ν = 0 level of the X 2 Σ + state of SiO + . We present a molecular model, including perturbations from the A 2 Π state, which explains the observed strong variation of fine structure as a function of rotational quantum number. These data yield greatly improved predictions of the microwave spectrum of the ground state of SiO + . In particular we predicted the ground state rotational transition (N = 2, J = 5/2) → (N = 1, J = 3/2) to be 86 063(1) MHz, confirming that this transition is not the source of the radio line known as U86.2 at 86 243.45(40) MHz.