Equilibria Between States of Discrete and Continuous Spectra

We calculate, in the small corrugation limit, the surface-acoustic phonon normal modes and the Brillouin scattering ripple cross-section for a grating on the Si(001) surface. Both the discrete and continuous spectra of acoustic modes have been studied within the elasticity theory. In the continuum the Rayleigh wave becomes a resonance and hybridizes with the longitudinal pseudo-mode of the flat surface, giving rise to a gap. The theory explains quantitatively recent experimental results.

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Oscillator-strength distribution in the discrete and continuous spectra of the alkali elements

Canadian Journal of Physics ◽

10.1139/p87-055 ◽

1987 ◽

Vol 65 (4) ◽

pp. 435-437 ◽

Cited By ~ 21

Author(s):

Carmen Barrientos ◽

Inmaculada Martin

Keyword(s):

Oscillator Strength ◽

Cross Sections ◽

Strength Distribution ◽

Quantum Defect ◽

Ionization Threshold ◽

Spectral Series ◽

Discrete And Continuous Spectra ◽

Alkali Elements

The oscillator-strength distribution between the discrete and continuous regions of the spectrum of the alkali elements Li, Na, K, Rb, and Cs has been obtained by following the quantum defect orbital (QDO) procedure. Continuity across the spectral-series limit has been found, and ionization-threshold cross sections are also reported.

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Atmospheric vertical energy flux due to a ground disturbance

Canadian Journal of Physics ◽

10.1139/p69-092 ◽

1969 ◽

Vol 47 (7) ◽

pp. 707-725 ◽

Cited By ~ 3

Author(s):

Robert F. MacKinnon

Keyword(s):

Energy Flux ◽

Acoustic Waves ◽

Ionospheric Disturbances ◽

Temperature Structure ◽

Temperature Profiles ◽

Perfect Gas ◽

Small Oscillations ◽

Leaky Modes ◽

Discrete And Continuous Spectra ◽

The Relationship

Evaluations are given of the nett mean vertical energy flux due to small oscillations at several altitudes caused by a ground disturbance in a wind- and temperature-stratified atmosphere. A theoretical model is assumed which consists of an inviscid perfect gas above a flat nonrotating earth. Results are given for various wind and temperature profiles. It is found that winds can appreciably affect the energy flux due to long-period waves at great heights. The importance of the temperature structure in the vicinity of critical levels is demonstrated. The significance of 'leaky' modes is discussed with regard to the relationship between the discrete and continuous spectra of waves. A simple approximation to energy flux associated with acoustic waves of short periods is found to apply for certain ground disturbances. The relevance of the results to traveling ionospheric disturbances is discussed.

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