Vibronic structure in triatomic molecules: The hydrocarbon flame bands of the formyl radical (HCO). A theoretical study

Abstract

A theoretical study of the vibrational structure of the X 2 AЈ ground and B 2 AЈ excited states of the formyl radical, HCO, and its deuterated form, DCO, has been performed. The potential energy surfaces have been computed by means of a multiconfigurational perturbative method, CASPT2. The computed geometries and the harmonic and anharmonic frequencies are successfully compared to the available experimental information. The vibrational intensities of the transition B 2 AЈ↔X 2 AЈ have been computed both for absorption and emission. The results lead to accurate determinations of several structural parameters and some reassignments of the vibrational transitions of the so-called hydrocarbon flame bands of the formyl radical.

Theoretical characterization of the lowest-energy absorption band of pyrrole

“…A full explanation of the procedure followed to obtain the vibronic intensities can be found elsewhere. 34,36 In order to account for the finite experimental resolution and for the degrees of freedom not considered here ͑such as rotation͒, the vibrational spectra computed in the present study were convoluted with a Lorentzian function of full width at half maximum ͑FWHM͒ corresponding to a lifetime of 33 fs. The temperature was considered by including a population of the vibrational states through a Boltzmann distribution at 10 K, therefore the presence of intense hot bands in the computed spectrum can be ruled out.…”

A new method of calculation of Franck–Condon factors which includes allowance for anharmonicity and the Duschinsky effect: Simulation of the He I photoelectron spectrum of ClO2

“…22,23 Recently, details of a few other types of anharmonic FCF methods have been published. [24][25][26][27][28] The major application of FCF calculations is in spectral simulation. Thus, it is worth mentioning the following recent studies, which are relevant to the present work.…”

Nonadiabatic orientation, toroidal current, and induced magnetic field in BeO molecules

“…Figure 2 shows the potential energy curves ⌬E i ͑R͒ = E i ͑R͒ − E 0 ͑R e,X ͒ of the electronic ground ͑i =0͒ and excited ͑i =1,2,3,...͒ singlet states ͉⌿ i ͘ of the BeO molecule, as calculated by means of the CASSCF͑6,12͒/CASPT2 method. 45,[48][49][50][51][52] We included six electrons and 12 orbitals in the active space and used an atomic natural orbital relativistic core correlated ͑ANO-RCC͒ 5s4p2d1f contracted basis set for both the Be-and the O-atom, including scalar relativistic effects by means of the Douglas-Kroll transformation. 53 The standard CASPT2 zeroth-order Hamiltonian was employed, 45 supplemented with an imaginary level shift parameter of 0.1E h to prevent intruder state problems.…”