Bond Modes

A local–normal description of vibrational excitations of pyramidal molecules in terms of Morse oscillators

“…Since several decades ago, local mode models have become relevant because they allow highly excited vibrational states to be characterized; they convey more insight into the nature of the eigenfunctions than the traditional approach of Darling-Dennison [7][8][9][10]. Local behavior is manifested by patterns with close degeneracies [11], easily noticed in systems with large differences in atomic masses, and nicely explained with the simplest version of the local theory [12].…”

Experimental and numerical exploration of intrinsic localized modes in an atomic lattice

“…Spectroscopic measurements on solids provide another way to search for an ILM feature. Evidence of ILMs have been reported in the analysis of resonant Raman spectra in the charge transfer solid PtCls [24], in the monatomic bcc crystal of 4 He where inelastic neutron scattering shows an anomalous optic-like mode [25], in single crystal alphauranium where a localized mode has been identified in the optic branch [26], in proteins where pico-second pump-probe measurements of the amide I band indicate a self-trapped vibrational state [27,28], and hydrogen-bonded acetanilide where spectral anomalies are interpreted as a signature of vibrational self trapping [29,30]. Each of these examples illustrates the fundamental experimental challenge of exploring ILMs in atomic solids; direct observation of 3-D energy localization is not yet possible and the observation of transitions, spectroscopic frequency shifts, or relaxation times of spectral elements are connected to localization by theoretical and numerical analysis.…”

“…The investigation of vibrational energy localization in highly excited small molecules has a long history, and a number of reviews have appeared [1][2][3][4][5][6][7]. Experiments on molecular overtone and combination bands by means of sensitive absorption, thermal lensing, and photoacoustic spectroscopy, particularly involving X-H vibrations, have been interpreted successfully in terms of normal modes for low-lying vibrational states and local modes for high-lying states.…”

Discrete breathers above phonon spectrum

“…These excitations are called as discrete breathers (DBs), intrinsic localized modes, vibrational solitons, or quodons [2,4,7,11,13,14,16,17,29,31,32,34,42,43,46,47,48,51,52]. In numerical studies of DBs different twobody potential models (Morse, Lennard-Jones, Born-MayerCoulomb and other potentials) have been used.…”