Repozytorium
Wyszukaj
Kolekcje
Inne
The ionic states of difluoromethane: A reappraisal of the low energy photoelectron spectrum including ab initio configuration interaction computations
Autorzy
Rok wydania
2017
Czasopismo
Numer woluminu
147
Strony
074305/1-074305/13
DOI
10.1063/1.4998150
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
A new synchrotron-based study of the photoelectron spectrum (PES) of difluoromethane is interpreted by an ab initio analysis of the ionic states, which includes Franck-Condon (FC) factors. Double differentiation of the spectrum leads to significant spectral sharpening; the vibrational structure observed is now measured with greater accuracy than in previous studies. Several electronic structure methods are used, including equation of motion coupled cluster calculations with single and double excitations (EOM-CCSD), its ionization potential variant EOM-IP-CCSD, 4th order Møller-Plesset perturbation theory (MP4SDQ) configuration interaction (CI), and complete active space self-consistent-field (CASSCF) methods. The adiabatic ionization energies (AIEs) confirm the assignments as band I, one state 12B1 (12.671 eV); band II, three states, 12B2 (14.259) < 12A1 (15.030) < 12A2 (15.478 eV); and band III, three states, 22B2 (18.055) < 22A1 (18.257) < 22B1 (18.808 eV). The three ionizations in each of the bands II and III lead to selective line broadening of the PES structure, which is attributed to vibronic overlap. The apparent lack of a vibrational structure attributable to both the 12A1 and 22A1 states in the PES arises from line broadening with the preceding states 12B2 and 22B2, respectively. Although these 2A1 states clearly overlap with their adjacent higher IE, some vibrational structure is observed on the higher IE. The effects of vibronic coupling are evident since the observed structure does not fit closely with the calculated Born-Oppenheimer FC profiles. Correlation of the lowest group of four AIEs in the PES of other members of the CH2X2 group, where X = F, Cl, Br, and I, clearly indicate these effects are more general.
Słowa kluczowe
Coupled-cluster methods, Ab initio configuration interaction, Correlation-consistent basis sets, Doppler effect, Vibrational spectra, Synchrotrons, Ions and properties, Photoelectron spectroscopy, Chemical compounds, Quantum chemical dynamics
Adres publiczny
http://dx.doi.org/10.1063/1.4998150
Strona internetowa wydawcy
Podobne publikacje
Accurate spectroscopic characterization of the HOC(O)O radical: A route toward its experimental identification
Puzzarini Cristina, Biczysko Małgorzata, Peterson Kirk A., Francisco Joseph S., Linguerri Roberto
Accurate molecular structures and infrared spectra of trans-2,3-dideuterooxirane, methyloxirane, and trans-2,3-dimethyloxirane
Barone Vincenzo, Biczysko Małgorzata, Bloino Julien, Puzzarini Cristina
Interpretation of the photoelectron, ultraviolet, and vacuum ultraviolet photoabsorption spectra of bromobenzene by ab initio configuration interaction and DFT computations
Palmer Michael H., Ridley Trevor, Hoffmann Søren Vrønning, Jones Nykola C., Coreno Marcello, de Simone Monica, Grazioli Cesare, Zhang Teng, Biczysko Małgorzata, Baiardi Alberto, Peterson Kirk