Jaho-Teller effect in tetrahedral symmetry:Large-amplitude tunneling motion and rovibronic structure of(CH4)+ and(CD4)+

摘要

The energy level structures of the ground vibronic states of 12(CH4)+,13(CH4)+,and 12(CD4)+ have been measured by pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy.The nuclear spin symmetries of the tunneling-rotational levels have been determined in double-resonance experiments via selected rotational levels of the upsilon3=1 and upsilon3=2 vibrational levels of the X 1Al ground state of CH4.The energy level structures of 12(CH4)+,13(CH4)+,and 12(CD4)+ have been analyzed with an effective tunneling-rotational Hamiltoniah.The analysis together with a group theoretical treatment of the T directX(e+t2)Jahn-Teller effect in the T_d(M)group prove that the equilibrium geometry of 12(CH4)+,13(CH4)+,and 12(CD4)+ has C_(2upsilon)symmetry and characterize the pseudorotational dynamics in these fluxional cations.The tunneling behavior is discussed in terms of the relevant properties of the potential energy surface,some of which have been recalculated at the CCSD(T)/cc-pVTZ level of ab initio theory.