nonpolarisen

Nonpolarisen, often referred to in astrochemistry and planetary science as nonpolar ice, denotes ices formed primarily from nonpolar or nearly nonpolar molecules, which have little or no permanent dipole moment. In contrast to polar ices that are rich in H2O, NH3, or CH3OH, nonpolar ices are dominated by species such as nitrogen (N2), carbon monoxide (CO), oxygen (O2), methane (CH4), and sometimes carbon dioxide (CO2). These ices form and persist at very low temperatures when these molecules condense on dust grains in interstellar environments or on icy bodies in the outer Solar System.

The interactions within nonpolar ices are governed largely by van der Waals forces, resulting in amorphous or, under certain conditions, crystalline structures. The physical state of the ice depends on temperature and deposition history, with amorphous forms common at the coldest conditions and crystallization occurring upon warming or annealing. Porosity and mixing with other ices can influence desorption and diffusion of molecules on grain surfaces.

Observationally, nonpolar ices display characteristic infrared absorption features corresponding to their vibrational modes, enabling their identification in astronomical spectra. Their presence affects the chemical evolution of icy mantles on dust grains and the volatile inventories of comets and outer Solar System bodies. Laboratory experiments simulate interstellar and planetary conditions to study phase behavior, spectral signatures, and desorption processes of nonpolar ices, informing models of astrochemical networks and planetary atmospheres.