Breathers or structural instability in solid L-alanine: A new IR and inelastic neutron scattering vibrational spectroscopic study

Mariette Barthes; Aasmund Fahre Vik; Alexandra Spire; Heloisa N. Bordallo; Juergen Eckert

doi:10.1021/jp015615c

Breathers or structural instability in solid L-alanine: A new IR and inelastic neutron scattering vibrational spectroscopic study

Mariette Barthes^*, Aasmund Fahre Vik, Alexandra Spire, Heloisa N. Bordallo, Juergen Eckert

^*Corresponding author for this work

56 Citations (Scopus)

Abstract

Incoherent Inelastic Neutron Scattering data and new infrared spectra were acquired in order to examine both the external and internal vibrations in crystalline L-alanine. For the first time we observe a splitting of the NH₃⁺ torsional band below a temperature of approximately 220 K as well as an overtone of this band. The intensity of both of these bands is strongly dependent on temperature. Birefringence and depolarization measurements performed with single crystals reveal a subtle breaking of symmetry around 220 K perhaps involving the hydrogen bond networks. We show that this instability cannot, however, be the origin of the observed splitting. Instead, the anomalous temperature dependence of the observed intensity and frequency of the torsional mode and its overtone may be explained on the basis of a nonlinear coupling of the NH₃⁺ oscillator with lattice phonons. This leads to localization of vibrational energy, a so-called "breather" or "vibrational polaron".

Original language	English
Journal	Journal of Physical Chemistry A
Volume	106
Issue number	21
Pages (from-to)	5230-5241
Number of pages	12
ISSN	1089-5639
DOIs	https://doi.org/10.1021/jp015615c
Publication status	Published - 30 May 2002
Externally published	Yes

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title = "Breathers or structural instability in solid L-alanine: A new IR and inelastic neutron scattering vibrational spectroscopic study",

abstract = "Incoherent Inelastic Neutron Scattering data and new infrared spectra were acquired in order to examine both the external and internal vibrations in crystalline L-alanine. For the first time we observe a splitting of the NH3+ torsional band below a temperature of approximately 220 K as well as an overtone of this band. The intensity of both of these bands is strongly dependent on temperature. Birefringence and depolarization measurements performed with single crystals reveal a subtle breaking of symmetry around 220 K perhaps involving the hydrogen bond networks. We show that this instability cannot, however, be the origin of the observed splitting. Instead, the anomalous temperature dependence of the observed intensity and frequency of the torsional mode and its overtone may be explained on the basis of a nonlinear coupling of the NH3+ oscillator with lattice phonons. This leads to localization of vibrational energy, a so-called {"}breather{"} or {"}vibrational polaron{"}.",

author = "Mariette Barthes and {Fahre Vik}, Aasmund and Alexandra Spire and Bordallo, {Heloisa N.} and Juergen Eckert",

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doi = "10.1021/jp015615c",

language = "English",

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TY - JOUR

T1 - Breathers or structural instability in solid L-alanine

T2 - A new IR and inelastic neutron scattering vibrational spectroscopic study

AU - Barthes, Mariette

AU - Fahre Vik, Aasmund

AU - Spire, Alexandra

AU - Bordallo, Heloisa N.

AU - Eckert, Juergen

PY - 2002/5/30

Y1 - 2002/5/30

N2 - Incoherent Inelastic Neutron Scattering data and new infrared spectra were acquired in order to examine both the external and internal vibrations in crystalline L-alanine. For the first time we observe a splitting of the NH3+ torsional band below a temperature of approximately 220 K as well as an overtone of this band. The intensity of both of these bands is strongly dependent on temperature. Birefringence and depolarization measurements performed with single crystals reveal a subtle breaking of symmetry around 220 K perhaps involving the hydrogen bond networks. We show that this instability cannot, however, be the origin of the observed splitting. Instead, the anomalous temperature dependence of the observed intensity and frequency of the torsional mode and its overtone may be explained on the basis of a nonlinear coupling of the NH3+ oscillator with lattice phonons. This leads to localization of vibrational energy, a so-called "breather" or "vibrational polaron".

AB - Incoherent Inelastic Neutron Scattering data and new infrared spectra were acquired in order to examine both the external and internal vibrations in crystalline L-alanine. For the first time we observe a splitting of the NH3+ torsional band below a temperature of approximately 220 K as well as an overtone of this band. The intensity of both of these bands is strongly dependent on temperature. Birefringence and depolarization measurements performed with single crystals reveal a subtle breaking of symmetry around 220 K perhaps involving the hydrogen bond networks. We show that this instability cannot, however, be the origin of the observed splitting. Instead, the anomalous temperature dependence of the observed intensity and frequency of the torsional mode and its overtone may be explained on the basis of a nonlinear coupling of the NH3+ oscillator with lattice phonons. This leads to localization of vibrational energy, a so-called "breather" or "vibrational polaron".

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DO - 10.1021/jp015615c

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SP - 5230

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JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory

IS - 21

ER -

Breathers or structural instability in solid L-alanine: A new IR and inelastic neutron scattering vibrational spectroscopic study

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