Excited state quantum phase transitions in the bending spectra of molecules

TL;DR

This paper extends the vibron model Hamiltonian to include all interactions up to four-body operators and applies it to model the bending spectra of fourteen molecules, revealing insights into excited state quantum phase transitions.

Contribution

It introduces a comprehensive Hamiltonian for the vibron model that captures diverse molecular bending behaviors within a unified algebraic framework.

Findings

Successfully modeled bending spectra of 14 molecules

Predicted quantum monodromy diagrams and energy plots

Demonstrated the model's flexibility across different molecular structures

Abstract

We present an extension of the Hamiltonian of the two dimensional limit of the vibron model encompassing all possible interactions up to four-body operators. We apply this Hamiltonian to the modeling of the experimental bending spectrum of fourteen molecules. The bending degrees of freedom of the selected molecular species include all possible situations: linear, bent, and nonrigid equilibrium structures; demonstrating the flexibility of the algebraic approach, that allows for the consideration of utterly different physical cases with a general formalism and a single Hamiltonian. For each case, we compute predicted term values used to depict the quantum monodromy diagram, the Birge-Sponer plot, the participation ratio. We also show the bending energy functional obtained using the coherent --or intrinsic-- state formalism.