A new set of potential energy surfaces for HCO: Influence of Renner-Teller coupling on the bound and resonance vibrational states

Abstract

It is commonly understood that the Renner-Teller effect can strongly influence the spectroscopy of molecules through coupling of electronic states. Here we investigate the vibrational bound states and low-lying resonances of the formyl radical treating the Renner-Teller coupled X̃(2)A(') and Ã(2)A(″) states using the MultiConfiguration Time Dependent Hartree (MCTDH) method. The calculations were performed using the improved relaxation method for the bound states and a recently published extension to compute resonances. A new set of accurate global potential energy surfaces were computed at the explicitly correlated multireference configuration interaction (MRCI-F12) level and yielded remarkably close agreement with experiment in this application and thus enable future studies including photodissociation and collisional dynamics. The results show the necessity of including the large contribution from a Davidson correction in the electronic structure calculations in order to appreciate the relatively small effect of the Renner-Teller coupling on the states considered here.

Resonance dynamics of DCO (X̃ A′2) simulated with the dynamically pruned discrete variable representation (DP-DVR)

“…However, theoreticians have used resonance calculations for HCO on the WKS surface as a benchmark case. [23][24][25][26][27][28] There, the deviations from the results of Ref. 22 have a similar magnitude as the deviations shown here.…”

A Mountaineering Strategy to Excited States: Highly Accurate Energies and Benchmarks for Medium Sized Molecules

“…There are detailed studies of the potential energy surfaces for the ground and lowest excited states of HCO. 172 For isoformyl, the convergence with respect to the basis set is fast and the lowest excited state is well converged with our FCI approach. Hence, we propose a safe TBE of 0.91 eV for the lowest vertical excitation.…”

Photoinduced C–H bond fission in prototypical organic molecules and radicals

“…propenyl and allyl radicals. The X and à states of the HCO radical are a Renner-Teller pair, 250 the H-CO bond is weak (D0(H-CO) = 50838 cm -1 ) and the photodissociation dynamics following excitation at visible wavelengths have been explored by measuring linewidths of the predissociating parent resonances, 251 the energy disposal in the resulting CO products, 252 the recoil anisotropies of the H and CO photofragments, 253 and by velocity map imaging 254 and HRA-PTS studies 255 of the H atom products. The last of these studies provides a particularly clear illustration of quantum interference effects in the decay of vibronically state selected HCO(A) radicals to H + CO(X, v, J) products.…”