Modelling the Vibration-Rotation Energy Levels of D218O molecule with Effective Hamiltonian Method

TL;DR

This paper analyzes the vibrational and rotational energy levels of the D218O molecule using various effective Hamiltonian models, achieving high accuracy and evaluating convergence properties.

Contribution

It introduces multiple forms of effective Hamiltonians for D218O and assesses their predictive accuracy and convergence, advancing molecular energy level modeling.

Findings

Accurate fitting of rotational constants close to experimental data

Evaluation of Hamiltonian models' predictive performance

Determination of convergence radii for Hamiltonian series

Abstract

Using the effective rotational Hamiltonian method, we have conducted an analysis of the D218O ground and the first excited vibration state rotational energy levels. The analysis was based on the effective Hamiltonians represented in several forms: the Watson Hamiltonian, the Hamiltonian expressed in terms of Pad\'e-Borel approximants, and the Hamiltonian in terms of generating function expansions. The rotational and centrifugal constants have been determined from the fitting, which describe the rotational energy levels with an accuracy close to that of the experimental data. The predictive performance of the model with respect to highly excited rotational states has been evaluated against the global variation calculations. The radii of convergence of the effective rotation Hamiltonian series have been determined.