Excitation Energies and Photoabsorption Oscillator Strengths of the Rydberg Series in CF₃Cl. A Linear Response and Quantum Defect Study

Abstract

Vertical excitation energies of the CF(3)Cl molecule have been obtained from a response function approach with a CC reference function to determine absolute photoabsorption oscillator strengths in the molecular-adapted quantum defect orbital formalism (MQDO). The present work covers more highly excited Rydberg states than have been experimentally reported. Assessing of the reliability of the present calculations is provided through a comparative analysis between the results of the molecule and the Cl atom. This can be used to allow for predictions of the same type of properties in other analogous systems.

Matrix isolation infrared spectroscopic and theoretical study of 1,1,1-trifluoro-2-chloroethane (HCFC-133a)

“…The doubly augmented orbitals (which are used to describe the Rydberg orbitals) have been centered on the Cl atom, based on previous results obtained for the CF 3 Cl molecule. 19,27,33 Similarly to what has been obtained for the CF 3 Cl molecule, preliminary results indicated that the location of the basis set used to describe the Rydberg orbitals is of secondary importance.…”

Accurate calculation of the ionization energies of the chlorine lone pairs in 1,1,1-trifluoro-2-chloroethane (HCFC-133a)

“…For the HCFC-133a molecule, a considerable admixture of Cl (Rydberg) and C (valence) orbitals is obtained, thus masking the assignment of the Rydberg orbitals. However, accurate calculations of the energies of the 4s and 4p Rydberg states and the ionization potential (IP) of the Cl lone pair yield quantum defects that are consistent with the values obtained for the s and p series of the chlorine atom [24][25][26].…”

“…It is important to mention that extensions of the previous calculations of 4s and 4p states [17] to include the Rydberg nd states-using, for instance, CASSCF/CASPT2 or CASSCF/ MR-CISD approaches-are computationally much more demanding, as both valence (3d) and Rydberg (4d) sets of Cl orbitals should be included in the active space, which can be justified by the fact that some of the configurations generated from the former set of d orbitals (e.g., n -3d) are likely to have lower energies than the corresponding configurations obtained from the latter set [25]. Thus, for molecules containing thirdrow elements, the use of Eq.…”

“…1 may be a reasonable alternative, especially if previous results suggest the use of known atomic quantum defects. For instance, in the case of HCFC-133a, a value of 0.16 is obtained from the average quantum defect of the Cl d orbitals [25], as the quantum defects for the ns and np Rydberg states of this molecule were found to be very close to those of the Cl atom [17]. Such a value, along with accurate values of the vertical ionization energies for the Cl lone pairs n 1 (A″) and n 2 (A′), can be used to obtain reasonable estimates for the energies of the nd Rydberg states through the use of Eq.…”

Full configuration interaction calculation of BeH adiabatic states

“…This type of basis sets has proven reliable for the calculation of vertical excitation energies ͑VEEs͒ in a number of cases that involved Rydberg states. 67,[71][72][73][74][75] The basis set here described will be denoted as ANO1 + 4s4p2d when necessary. The 4s4p2d Rydberg AOs are reported in Table I.…”