No abstract

A special type of interaction between conduction electrons and Frenkel excitons in magnetic or organic semiconductors different from the usual polarization interaction is described. It consists in that the transitions of the conduction electron from one atom to another are accompanied by the creation or annihilation of an exciton a t one of these atoms. Furthermore, transitions of the electron from non-excited to excited atoms are possible which are accompanied by exciton transitions in the opposite direction. As a result of the interaction, specific states of charge carriers called transferons arise which differ strongly from excitonic polarons. An expression for self-energy and damping of the transferon is obtained in the limit of weak electron-exciton coupling.Es wird eine spezielle Wechselwirkung zwischen Leitungselektronen und Frenkelexzitonen in magnetischen oder organischen Halbleitern bescbxieben, die verschieden ist von der normalen Polarisationswechselwirkung. Sie besteht darin, daI3 die Ubergange der Leitungselektronen von einem Atom zum anderen verknupft sind mit der Bildung und Annihilation eines Exzitons an einem dieser Atome. Dariiber hinaus sind Ubergange des Elektrons Ton nichtangeregten zu angeregten Atomen moglich, die von ExzitonenubergLngen in entgegengesetzter Richtung begleitet werden. Als Ergebnis der Wechselwirkung treten spezielle Zustande der Ladungstrager, sogenannte Transferonen auf, die sich stark von Exzitonenpolaronen unterscheiden. Ein Ausdruck fur Selbstenergie und Dampfung der Transferonen wird fur den Grenzfall schwacher Elektron-Exziton-Kopplung abgeleitet.

543.423;533.9 The spectral and temporal characteristics of plasmas produced by femtosecond laser pulses acting on seawater surfaces are studied. The time dependence of the decay in the intensities of emission lines and the continuum are determined and the electron density is estimated using the three-body recombination time. It is shown that an atomic line with a low excitation potential is the most sensitive for femtosecond laser induced breakdown spectroscopy.Introduction. The increasing anthropogenic effect on the world's oceans has created a need for the development of new methods for monitoring marine ecosystems. Laser induced breakdown spectroscopy (LIBS) is definitely one such operational technique. LIBS does not require advanced preparation of samples, can be used for spectral analysis in real time, is a contactless, remote analysis technique, and can be used to determine the concentrations of a wide range of elements with relatively small sample sizes. The use of LIBS for determining the elemental composition of seawater was first proposed in [1,2]. Further studies have established the optimal parameters for detection of the emission lines of the elements dissolved in seawater with breakdown by nanosecond laser pulses [3-10]. The detection limits for elements by this method of laser plasma excitation is ~10