The multiphoton ionization spectra of several arene molybdenum tricarbonyls have been measured in the region 350–420 nm. These spectra exhibit allowed, two-photon resonant ns ${}_{}{}^7{}_{}{}^{}$${\mathit{S}}_3$ and nd ${}_{}{}^7{}_{}{}^{}$${\mathit{D}}_{\mathit{J}}$ Rydberg series of neutral bare molybdenum atoms. Furthermore, the electric field inherent to the multiphoton ionization experiment also permits observation of the nominally forbidden np ${}_{}{}^7{}_{}{}^{}$P${\mathrm{°}}_{\mathit{J}}$ Rydberg series. A nonlinear least-squares regression of the Rydberg equation was used to obtain an improved ionization potential of molybdenum and the quantum defects of the three series.

• Received 12 May 1988

DOI:https://doi.org/10.1103/PhysRevA.38.3498