Multiphoton excitation and subsequent ionization detection of metastable atoms: measurement of n3S-n3D splittings in He.

A simple technique is described for the efficient detection of multiphoton transitions from metastable states of atomic or molecular species to their excited states of either even or odd parity. This technique is demonstrated in metastable He, and first measurements of n3S-n3D splittings for n = 18-22 are reported.