Conformity of the 7-azaindole dimer cationic potential with photoionization/Coulomb-explosion MS observations and the concerted biprotonic transfer mechanism

In this Letter we consider the second laser-pulse time delay experiments of Castleman and co-workers [D.E. Folmer, L. Poth, E.S. Wisniewski, A.W. Cast Ieman, Jr., Chem. Phys. Lett. 287 (1998) 1; D.E. Folmer, E.S. Wisniewski, S .M. Hurley, A.W. Castleman, Jr., Proc. Natl. Acad. Sci. USA 96 (1999) 12980 ] as interrogating the (density functional theory) biprotonic phototautomer ization as correlated with the cationic doublet ground electronic state pot ential D-0((+)) for the species produced in the photoionization step. We de monstrate that the 7-AI(H+) cation can result as a product of this photoion ization, and is then revealed a Coulomb-explosion time-of-flight mass spect rum (TOF-MS) species. We demonstrate that the mass-119/mass-118 ratios as a function of photoionization, and Coulomb-explosion laser pulse delay can c onform to the concerted biprotonic mechanism. The interpretation emphasizes the invasive nature of the TOF-MS technique requirement in studying the ex cited state of the doubly-H-bonded 7-azaindole dimer. (C) 2000 Elsevier Sci ence B.V. All rights reserved.