The rise of an exciton in solid ammonia

Andrew Cassidy; Rachel L. James; Anita Dawes; David Field

doi:10.1039/d1cc05520h

The rise of an exciton in solid ammonia

Andrew Cassidy^*, Rachel L. James, Anita Dawes^*, David Field

^*Corresponding author af dette arbejde

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avis › Tidsskriftartikel › Forskning › peer review

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Abstract

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.

Originalsprog	Engelsk
Tidsskrift	Chemical Communications
Vol/bind	58
Nummer	6
Sider (fra-til)	815-818
Antal sider	4
ISSN	1359-7345
DOI	https://doi.org/10.1039/d1cc05520h
Status	Udgivet - 18 jan. 2022

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10.1039/d1cc05520hLicens: CC BY-NC

d1cc05520hForlagets udgivne version, 1,98 MBLicens: CC BY-NC

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title = "The rise of an exciton in solid ammonia",

abstract = "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.",

author = "Andrew Cassidy and James, {Rachel L.} and Anita Dawes and David Field",

note = "Publisher Copyright: This journal is {\textcopyright} The Royal Society of Chemistry",

year = "2022",

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T1 - The rise of an exciton in solid ammonia

AU - Cassidy, Andrew

AU - James, Rachel L.

AU - Dawes, Anita

AU - Field, David

PY - 2022/1/18

Y1 - 2022/1/18

N2 - 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.

AB - 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.

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U2 - 10.1039/d1cc05520h

DO - 10.1039/d1cc05520h

M3 - Journal article

C2 - 34928278

AN - SCOPUS:85123585248

SN - 1359-7345

VL - 58

SP - 815

EP - 818

JO - Chemical Communications

JF - Chemical Communications

IS - 6

ER -

The rise of an exciton in solid ammonia

Abstract

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