An algebraic alternative for the accurate simulation of CO₂ Raman spectra

Abstract

We present an accurate simulation of the Raman spectrum of the carbon dioxide molecule in the 1150–1500 cm−1 spectral range, comparing the results obtained using the three polyad schemes found in the literature of this molecule. The description of the molecule with the algebraic U1(2)×U(3)×U2(2) local model encompasses both stretching and bending degrees of freedom. A detailed analysis of the Hamiltonian interactions for the three polyad schemes provides fittings with root mean square deviations in the range 0.14–0.20 cm−1, involving 19 parameters taking into account the 178 experimental term energies found in the literature. Using a limited subset of 9 experimental transition moments, we optimize 5 partial derivatives of the mean polarizability and simulate the Raman spectrum of CO2 for the three polyad schemes. Comparing the calculated results with the experimental spectrum, we obtain an overall good agreement for the three polyads. However, an inspection in detail of the spectrum seems to show a slight preference for polyad P212 albeit not due to the interaction characterizing the polyad but due to anharmonic effects and energy distribution. Finally, we assess the effect of the Fermi resonance over CO2 Raman line intensities.

Anharmonicity-induced excited-state quantum phase transition in the symmetric phase of the two-dimensional limit of the vibron model

“…Therefore, the 2DVM can tackle the feature-rich large-amplitude bending spectrum of nonrigid species [55,56]. This approach has also been used to model coupled benders [57][58][59] or the coupling between bending and stretching degrees of freedom [60][61][62][63].…”

Quantum fidelity susceptibility in excited state quantum phase transitions: application to the bending spectra of nonrigid molecules

“…An extension to four-body operators of the algebraic Hamiltonian, used in the present work, has been recently published [34]. The 2DVM has also been used for the modeling of coupled benders [28,[35][36][37], stretch-bend interations [38][39][40][41], and the transition state in isomerization reactions [42].…”

Excited state quantum phase transitions in the bending spectra of molecules

“…An extension to four-body operators of the algebraic Hamiltonian, used in the present work, has been recently published [33]. The 2DVM has also been used for the modeling of coupled benders [27,[34][35][36], stretch-bend interations [37][38][39][40], and the transition state in isomerization reactions [41].…”