The preparation of methyl iodide (CH3I) in selected rovibrational states [nu(7)=1 (C-H stretch); J] by infrared (IR) excitation prior to vacuum ultraviolet (VUV) photoionization has greatly simplified the observed pulsed field ionization-photoelectron (PFI-PE) spectra, allowing the direct determination of the rotational constants B+(C+)=0.254+/-0.003 cm(-1) for CH3I+((X) over tilde E-2(3/2);nu(7)(+)) and the ionization energy (76 896.9+/-0.2 cm-1) for CH3I+((X) over tilde E-2(3/2);nu(7)(+)=1,J(+)=3/2)<--CH3I((X) over tilde (1)A(1);nu(7)=1,J=0). The IR-VUV-PFI-PE and IR-VUV-photoion measurements also provide relative state-to-state (nu(7)(+)=1, J(+)<--nu(7)=1, J) cross sections for the photoionization process. (C) 2004 American Institute of Physics.