Theoretical Study On Photoelectron Spectrum Of BCl₃⁺ Cation In The C²A₂" State

Boron Trichloride(BCl3)is one of important etching gases,and its ionization and dissociation properties and accurate physical chemistry data are very significant for the related industrial applications.The spectra and dynamics of BCl3+ ions inthe ground and excited stateshave been studied for a long time,and the relevant experimental and theoretical data are quite sufficient.However,compared with BCl3+cation in ground state,X2A2’,the investigations on the electronically excited state,C2A2",is relatively lackng,and most of them are basically focusedon the experimental measurements,and the correspondingtheoretical calculations and mechanisms are insufficient,even adiabatic ionization energy(AIE)and vibrational assignments of photoelectron spectrumare far from reliable results.In this work,density functional theory(DFT)has been applied to in-depth study photoelectron spectrum of BCl3+ cation in the C2A2" State.With the aug-cc-pvtz basis set,geometries of neutral BCl3,BCl3+cation in ground state,X2A2’,and theelectronically excited state,C2A2",were optimized using three DFT levels,i.e.PBE0,ωB97XD,and M06-2X.The corresponding harmonic vibrational frequencies and the Franck-Condon factors of the BCl3(X1A1)→BCl3+(C2A2" transition were then calculated,and the photoelectron spectrum was simulated.For neutral BCl3,BCl3+ cation in ground state,X2A2’,and theelectronically excited state,C2A2",the orbital electron cloud distributions,bond lengths,bond angles,vibration modes and frequencieswerecalculated with their respective optimized structures.Then,according to the Franck-Condon factors of the BCl3(X1A1)→BCl3+(C2A2")transition,the dominant vibrational excitation modeswere determined during this ionization process.All these detailed calculations make the present calculations self-consistent.By comparing with high-resolution photoelectron spectrum previously recorded in experiment,we have successfully simulated the photoelectron spectrum of the C2A2" band,and have obtained reliable assignments for the observed vibrational progression.Based on these vibrational assignments,the adiabatic and vertical ionization energies for BCl3+cation in the C2A2" state have directly been determined to beAIE(C2A2")=14.298±0.028 eV and VIE(C2A2")=14.405±0.028 eV,respectively,and herein,thosewrong values in previous studieshave been corrected.