Aarhus University Seal

The rise of an exciton in solid ammonia

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


We trace a polymorphic phase change in solid ammonia films through the emergence of a Frenkel exciton at 194.4 nm, for deposition temperatures of 48 K, 50 K and 52 K. Observations on a timescale of hours give unparalleled access to the individual processes of nucleation and the phase change itself. The excitonic transition is forbidden in the low temperature phase, but greater flexing of the solid state structure in the higher temperature phase makes the transition allowed, as the nano-crystals approach ∼30 unit cells through nucleation. We find activation energies of 21.7 ± 0.6 kJ mol−1 for nucleation and 22.8 ± 0.6 kJ mol−1 for the phase change, corresponding to the breaking of two to three hydrogen bonds.

Original languageEnglish
JournalChemical Communications
Pages (from-to)815-818
Number of pages4
Publication statusPublished - 18 Jan 2022

Bibliographical note

Publisher Copyright:
This journal is © The Royal Society of Chemistry

See relations at Aarhus University Citationformats

ID: 272747796