Physical properties of methanol (CH$_3$OH) ice as a function of temperature: Density, infrared band strengths, and crystallization

TL;DR

This study investigates how the physical properties of methanol ice, including density, infrared spectral features, and crystallization behavior, vary with temperature under simulated interstellar conditions, providing new data for astrophysical models.

Contribution

It offers new measurements of methanol ice density, IR band strengths, and insights into the amorphous-to-crystalline transition, enhancing understanding of interstellar ice properties.

Findings

Density of methanol ice varies with temperature.

IR band strengths are quantified at different temperatures.

Crystallization of methanol ice occurs during warm-up.

Abstract

The presence of methanol among the common ice components in interstellar clouds and protostellar envelopes has been confirmed by the James Webb Space Telescope. Methanol is often detected in the gas phase toward lines of sight shielded from UV radiation. We measured the volumetric density of methanol ice, grown under simulated interstellar conditions, and the infrared spectroscopy at different deposition temperatures and during the warm-up. The IR band strengths are provided and the experimental spectra are compared to those computed with a model. The transition from amorphous to crystalline methanol ice was also explored. Finally, we propose new observations of methanol ice at high resolution to probe the methanol ice structure.