First-principles simulations of transition state spectra of the I plus HI and I plus DI reactions and vibrational bonding in IMuI

The lowest three potential energy surfaces for the I(P-2(3/2), P-2(1/2)) + HI(X-1 Sigma) reaction have been developed using extensive ab initio electronic structure calculations including the spin-orbit interaction. Using the ab initio potential energy surfaces, we simulate experimentally-observed transition state spectra for the I + HI and I + DI reactions by calculating photodetachment spectra of the IHI and IDI anions. Very good agreement was obtained between theory and experiment. When the hydrogen atom is replaced by Mu, which is a very light isotope of hydrogen, it was found that the I + MuI reaction system has a bound vibrational-bonding state whose wavefunction is highly localized around the transition state region on the ground-state potential energy surface. All other systems containing heavier hydrogen isotopes show only a van der Waals bonding feature. (C) 2015 Elsevier B.V. All rights reserved.