The single-photon pulsed field ionization photoelectron (PFI-PE) spectrum of trans-2-butene (trans-CH3CH=CHCH3) in the energy range of 73 500-75 850 cm-1 has been measured using vacuum ultraviolet laser sources. The semi-empirical simulation of fine structures resolved in the original PFI-PE band yields a value of 73 624.7+/-2.0 cm(-1) for the ionization energy (IE) of trans-2-butene. The vibrational bands for trans-CH3CH=CHCH3+ resolved in the PFI-PE spectrum are assigned based on ab initio calculations of the vibrational frequencies and Franck-Condon factors (FCFs) for ionization transitions. This assignment has provided reliable vibrational frequencies (nu(1)(+)=104 cm(-1), nu(2)(+)=127 cm(-1), nu(3)(+)=131 cm(-1), nu(5)(+)=484 cm(-1), nu(8)(+)=798 cm(-1), nu(13)(+)=1164 cm(-1), nu(14)(+)=1264 cm(-1), nu(16)(+)=1307 cm(-1), nu(20)(+)=1407 cm(-1), and nu(22)(+)=1567 cm(-1)) for trans-CH3CH=CHCH3+. The PFI-PE spectrum is compared to the recently reported PFI-photoion (PFI-PI) spectrum for trans-2-butene. The major difference observed between the PFI-PE and PFI-PI spectra is that the intensities for excited vibrational bands were significantly suppressed or indiscernible in the PFI-PI spectrum, suggesting that the lifetimes for high-n Rydberg states associated with these excited vibrational bands were greatly reduced under the conditions used in the PFI-PI study. The experimental conditions used in the PFI-PI study also led to an IE value of about 20 cm-1 lower than that obtained in the PFI-PE measurement. We have also reassigned the vibrational bands resolved in the PFI-PE spectrum for cis-2-butene based on the FCF calculation and a more reliable set of theoretical vibrational frequencies. (C) 2003 American Institute of Physics.