Atomic momentum distributions in polyatomic molecules in rotational-vibrational eigenstates

TL;DR

This paper introduces a quantum mechanical method to calculate atomic momentum distributions in polyatomic molecules, revealing oscillatory behaviors linked to quantum delocalization in specific molecular states.

Contribution

A novel quantum mechanical approach for atomic momentum distributions in polyatomic molecules, with detailed analysis of oscillations due to atomic delocalization.

Findings

Oscillatory changes in proton momentum distribution in H2O

No such oscillation in linear CO2 molecules

Oscillations originate from quantum delocalization of atoms

Abstract

We report a quantum mechanical method for calculating the momentum distributions of constituent atoms of polyatomic molecules in rotational-vibrational eigenstates. Application of the present theory to triatomic molecules in the rovibrational ground state revealed that oscillatory changes appear on the proton momentum distribution in the nonlinear $\mathrm{H_2O}$ molecule, whilst no such modulation is present in the case of an oxygen atom in the linear $\mathrm{CO_2}$ molecule. The atomic momentum distributions were analyzed in detail by means of a rigid rotor model, and it was found that the oscillation originates from quantum-mechanical delocalization of the target atom with respect to the other atoms.