On the mechanism of the energy redistribution in the A 2Ag(2Σg+) state of the HCCH+ ion

✍ Scribed by G. Chambaud; R. Van den Boom; P. Rosmus

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 433 KB
• Volume: 247
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(95)01188-2

✦ Synopsis

Using ab initio calculations large parts of the six-dimensional potential energy functions for all electronic components of 2 + and ,~' states of the acetylene radical cation have been mapped. It has been found that the lowest the X 21]u, A Xg 2IIg doublet state of HCCH + is not the trans-bent A 2Ag(2~g+) state, as expected, but the cis-bent ,~' 2AE(2[Ig) shake-up state, which is not Franck-Condon active in the ionization process because of its long Rcc distance. The A state has only one trans-bent (2Ag) minimum, the ,~' state has three minima (two cis-bent (2A2 and 2B2) and one trans-bent ( )) on the adiabatic potential energy functions. The three X 2IIu, A 2E+ and ,~' 2IIg electronic states are vibronically coupled in the conical intersection regions lying close to the equilibrium structure of the ~. 2Ag(2,~,~-) state by the v3, v4 and v5 modes, which explains why all experimentally observed vibrational bending modes have lifetimes in the range of only 150 to 2 ps.