Disentangling the Complex Vibrational Spectrum of the Protonated Water Trimer, H+(H2O)(3), with Two-Color IR-IR Photodissociation of the Bare Ion and Anharmonic VSCF/VCI Theory

作者：Duong Chinh H; Gorlova Olga; Yang Nan; Kelleher Patrick J; Johnson Mark A^*; McCoy Anne B^*; Yu Qi; Bowman Joel M^*

来源：Journal of Physical Chemistry Letters, 2017, 8(16): 3782-3789.

DOI：10.1021/acs.jpclett.7b01599

Vibrational spectroscopy of the protonated water trimer provides a stringent constraint on the details of the potential energy surface (PES) and vibrational dynamics governing excess proton motion far from equilibrium. Here we report the linear spectrum of the cold, bare H+(H2O)(3) ion using a two-color, IR-IR photofragmentation technique and follow the evolution of the bands with increasing ion trap temperature. The key low-energy features are insensitive to both D-2 tagging and internal energy. The D-2-tagged D+(D2O)(3) spectrum is reported for the first time, and the isotope dependence of the band pattern is surprisingly complex. These spectra are reproduced by large-scale vibrational configuration interaction calculations based on a new full-dimensional PES, which treat the anharmonic effects arising from large amplitude motion. The results indicate such extensive mode mixing in both isotopologues that one should be cautious about assigning even the strongest features to particular motions, especially for the absorptions that occur close to the intramolecular bending mode of the water molecule.

• 出版日期2017-8-17