Quantum state resolved pulsed field ionization-photoion (PFI-PI) spectra of several small molecules have been obtained, and a few state-selected and kinetic energy selected ion molecule reactions have been studied in detail in this dissertation. Tunable vacuum ultraviolet (VUV) laser is employed, along with a PFI-PI double-quadrupole double-octupole (DQDO) mass spectrometer to conduct these spectroscopic and chemical dynamics studies. Electronic, vibrational, and rotational selected ions are produced by direct photoexcitation with intense, high-resolution VUV laser to high-n Rydberg states, then field ionized by external pulsed electric fields. Pulsed electric field sequences, including their intensity and duration, are adjusted for each unique molecular ion studied to achieve ion beam kinetic energy resolution of as good as 0.05 eV in the lab frame (E[subscript lab]). Kinetic energy dependent integral cross section measurements are measured in the center-of-mass kinetic energy (E[subscript CM]) range of 0.05 – 10.0 eV. Octupole ion guides are used to transmit reactant and product ions from the source to the mass spectrometer with high transmission efficiency. Quadrupole mass spectrometer is used to selectively transmit ions with specific mass to charge ratio. It is demonstrated a wide range of molecular species can be studied in the present VUV-PFI-PI-DQDO apparatus. In this dissertation, N2+, CH4+, O2+, H2+, H2O+, as well as a transition metal ion V+ are investigated spectroscopically and kinetically. Some quantum state resolved photoions are produced for the first time (e.g. rotational selected H2+, electronically and vibrational selected O2+, and spin-orbit state selected V+). Ion-molecule reactions involving these molecular ions are studied and quantum state effects on their reactivity are noticed and discussed. These include the vibrational state and kinetic energy dependence of the product channels and cross sections of reaction N2+(X2[sigma][subscript g], v+=0-2) + C2H2, the rotational enhancement and more complicated vibrational effects of reaction H2O+(X2B1, v1+v2+v3+, N+[subscript Ka+Kc+]) +HD, the distinctive charge transfer cross sections of O2+(a4[pi][subscript u], X2[pi][subscript g], v+)+Ar with reactant ions in two different electronic states while close in total internal energy, and the vibrational and rotational enhancement of proton transfer reaction of H2+(X2[sigma][subscript g]+, v+=1-3, N+=0-3)+Ne. For the CH4/CH4+ system, it is also shown that through studying the unimolecular dissociation dynamics by the PFI-PI method, thermochemistry data, e.g. appearance energy (AE) and bond dissociation energy (D0), can be obtained with unprecedented accuracy.