Photoionization of methanol dimer using a tunable vacuum ultraviolet laser

Methanol dimer (CD3OH)2 ion–molecule reaction is initialized by VUV ~vacuum ultraviolet! laser photoionization. The proton and deuteron transfers are the dominant reactions. The relative probabilities of deuteron transfer from the methyl group and proton from the hydroxyl group were measured as a function of VUV photon energy between 10.91 to 10.49 eV. According to those results, the probability of proton transfer from the hydroxyl group increases with the VUV photon energy. Isotopic scrambling is not complete before dissociation of the ion complex in the photon energy used. In addition, ab initio calculations are performed and four stable structures of the methanol dimer ion are found. One of these structures is an unreported complex, CD3OHD 1 ̄CD2OH, which has a very unusual type of hydrogen bond. This complex plays a significant role in the deuteron transfer reaction in the range of excitation energies used in this study. © 1999 American Institute of Physics. @S0021-9606~99!00832-6#