Atomic swelling upon compression

TL;DR

This paper investigates how a hydrogen atom unexpectedly expands in size under high pressure confinement, revealing a novel swelling effect that alters its physical properties.

Contribution

It introduces the phenomenon of atomic swelling under spherical confinement, challenging the conventional expectation of atomic shrinking under compression.

Findings

Atomic size increases significantly upon swelling.

Photoabsorption properties change notably with swelling.

Swelling occurs when confinement radius drops below a critical value.

Abstract

The hydrogen atom under the pressure of a spherical penetrable confinement potential of a decreasing radius $r_{0}$ is explored, as a case study. A novel counter-intuitive effect of atomic swelling rather than shrinking with decreasing $r_{0}$ is unraveled, when $r_{0}$ reaches, and remains smaller than, a certain critical value. Upon swelling, the size of the atom is shown to increase by an order of magnitude, or more, compared to the size of the free atom. Examples of changes of photoabsorption properties of confined hydrogen atom upon its swelling are uncovered and demonstrated.