Two photon laser spectroscopy of indium

Two photon transitions from the 5 2P0½ and 5 2P03/2 states of In have been observed to high lying 2P0 and 2F0 states. Extended series corresponding to P0 → nP0 and P0 → nF0 transitions are seen to n = 23 and n = 31 res­pectively. A hybrid resonance through intermediate states of In2 gives rise to a series 6s2S → np 2P0 which can be followed to n = 42. Resonant en­hancement of the 52P03/2 → np2P0 series occurs because of an intermediate 2S state. This produces a singularity in the cross section for this transition. Possible two photon transitions to autoionizing states of In are also seen.