The drop analyser, also termed the tensiograph, is an optical fibre-based instrument system for monitoring liquids. A comprehensive assessment of the drop analyser used as a UV-visible spectrophotometer has been undertaken employing both experimental and theoretical studies. A model of the tensiograph signal (tensiotrace) has been developed using a ray-tracing approach to accurately predict the form of the tensiotrace as an aid to drop spectroscopy. An analytical equation is derived for quantitative drop spectroscopy and the form of the equation has been experimentally tested. The equation applies to both the case of a growing drop and the situation in which the drop volume is held stationary. Measurements on both stationary and moving drops are of practical value. Modelling has been used to compute the average path length of the coupled light in the drop to give a result that compares favourably with values obtained from experimental measurements. An optimized method has been identified for quantitative drop spectroscopy measurements. Results from UV-visible studies on both pollutants in water and pharmaceuticals demonstrate the utility of this approach. Two key matters relating to the practicalities of drop spectroscopy are then discussed. Some experimental studies have been made to ascertain the practical limit in analyte concentration above which variations in transmitted light from the drop shape variations result. Here, tabulated information on a representative range of liquid types has been provided as a guide to optimized spectroscopic drop analysis. Secondly, the handling of micro-volume samples is discussed. The paper concludes with a brief evaluation of the usefulness of this drop spectroscopy approach, but specifically points to the importance of drop spectroscopy for nanoscience applications.

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The stationary wave functions of fast electrons axially channeling in the silicon crystal near [110] direction have been found numerically for integrable and non-integrable cases, for which the classical motion is regular and chaotic, respectively. The nodal structure of the wave functions in the quasi-classical region, where the energy levels density is high, is agreed with quantum chaos theory predictions.

TunnelingT h e q u a n t iz a t io n o f t h e t r a n s v e r s e m o t io n e n e r g y in t h e c o n tin u o u s p o t e n t ia ls o f a t o m ic s trin g s a n d p la n e s ca n ta k e p la c e u n d e r p a s s a g e o f fa s t c h a r g e d p a r tic le s th r o u g h c ry s ta ls . T h e e n e r g y le v e ls fo r e le c tr o n m o v in g in a x ia l c h a n n e lin g r e g im e in a s IntroductionThe motion o f a fast charged particle in a crystal near one of crystallographic axes or planes is determined mainly by the contin uous potential that is the potential o f a crystal lattice averaged along the axis or plane, near which the motion takes place. The longitudinal component o f the particle's momentum parallel to the crystallographic axis or plane is conserved in such field. So, the problem on the particle's motion in a crystal is reduced to the two-dimensional problem o f its motion in the transverse plane. The finite motion in the potential wells formed by the continuous potentials o f atomic axes or planes is known as axial or planar channeling, respectively (see [1][2][3][4][5][6][7] and references therein).The electron motion under axial channeling described by classical equation o f motion can be both regular and chaotic. A pronounced example o f chaotic behavior is axial channeling in a continuous potential created by two neighboring atomic strings [110] o f diamond-like crystal [3,4].On the other side, the quantum effects can manifest themselves during channeling. Particularly, the quantization o f the transverse motion energy can take place (see, e.g. [3, Ch. 7, Sec. 53],[5, Sec. II C]). Investigation o f the chaotic behavior on quantum level needs statistical analysis o f large massive o f energy levels (thousands or more) [8]. Many numerical methods for searching the transverse motion energy levels as well as other quantum characteristics o f a particle motion in channeling regime had been developed in the pioneering papers on quantum approach to channeling phenome non (a good review o f them could be found in the book [6]). E -m ail address: syshch@yandex.ru (V.V. Syshchenko). 0168-583X/S -see fron t m atter

The Smith-Purcell radiation is usually measured when an electron passes over the grating of metallic stripes. However, for high frequencies (exceeding the plasma frequency of the grating material) none material could be treated as a conductor, but ought to be considered as a dielectric with plasma-like permittivity. So for describing Smith-Purcell radiation in the range of high frequencies new theoretical approaches are needed. In the present paper we apply the simple variant of eikonal approximation developed earlier to the case of radiation on the set of parallel semi-infinite dielectric plates. The formulae obtained describe the radiation generated by the particles both passing through the plates (traditionally referred as "transition radiation") and moving in vacuum over the grating formed by the edges of the plates (traditionally referred as "diffraction radiation", and, taking into account the periodicity of the plates arrangement, as Smith-Purcell radiation).