A plane parallel model of multipactor is studied in detail using both an analytical approach and numerical simulations. The analytical analysis is carried out within a widely exploited approximation, which assumes a fixed value for the initial velocity of secondary electrons. It is shown that the commonly accepted picture of the multipactor zones is not quite complete and should be modified by taking into account the existence of hybrid resonance modes and the important consequences of a secondary emission yield that significantly exceeds unity. Numerical simulations demonstrate that the chart of the multipactor zones is also very sensitive to a spread of the initial velocity of the electrons. In particular, the full effect of initial electron velocities cannot accurately be modeled by using a single fixed value only.

An analytical and numerical investigation is made of the multipactor phenomenon in a simple one-dimensional metallic gap exposed to a homogeneous rf field consisting of two carrier waves with close but separated frequencies. It is shown that in contrast to the monochromatic case (i.e., single carrier operation), the time varying envelope resulting from the beating of the two carrier waves leads to a suppression of multipactor breakdown, if appropriate combinations of carrier amplitudes and frequency separation are chosen. Furthermore, this combination depends neither on gap width nor on frequency range. Based on these results it is possible to draw the tentative conclusion that the regime of multicarrier operation is very promising from the point of view of avoiding breakdown. This is particularly so in systems of complicated geometry where single carrier operation may lead to multipactor breakdown for any high level of rf power.

SURFACES, INTERFACES, LIQUIDS AND THIN FILMS C410 depth profile the surface disorder and possible pressure induced phase transitions. The results indicate that all of the studied compounds were changed due to the compression. The GID analysis shows that the surface regions of the compacted tolbutamide, carbamazepine and chlorpropamide tablets were disordered. The manifestations of the disordering in the diffractographs are the increased peak intensity and height and the decreased peak width. Moreover, a polymorphic phase transition was observed in chlorpropamide tablets. The biggest changes took place at the very surface of the tablets. The transitions were also dependent on the used compaction pressure.

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Введение В нàñòîящåå âрåмя рàмàнîâñêàя ñпåêòрîñêîпия или ñпåêòрîñêîпия êîмáинàциîннîгî рàññåяния (ÊР) ñâåòà яâляåòñя мîщным инñòрóмåнòîм для иññлåдîâàния рàçли÷ныõ âåщåñòâ. Сâîå ширîêîå рàñпрîñòрàнåниå îнà пîлó÷илà áлàгîдàря âîçмîжнîñòи нåрàçрóшàющåгî иçó÷åния рàçнîîáрàçныõ îáъåêòîâ â рàçли÷ныõ àгрåгàòныõ ñîñòîянияõ. ÊР ñпåêòрîñêîпия ñ óñпåõîм иñпîльçóåòñя â гåîлîгии и минåрàлîгии, гåммîлîгии, áиîлîгии и мåдицинå, êриминàлиñòиêå, à òàêжå â рàç-ли÷ныõ îòрàñляõ прîмышлåннîñòи. Цåль дàннîй рàáîòы çàêлю÷àлàñь â иññлåдîâàнии фàçîâîгî пåрåõîдà жидêîñòь-êриñòàлл, îпрåдåлåнии мåòàñòàáильнîй îáлàñòи â рàйîнå òî÷êи нàñыщåния и âыяâлåнии прåдêриñòàллиçàциîнныõ êлàñòåрîâ â âîднî-ñîлåâîм рàñòâîрå â рàмêàõ êâàòàрîннîй êîнцåпции ñàмîîргàниçàции âåщåñòâà [1]. В êà÷åñòâå мîдåльнîгî îáъåêòà иñпîльçîâàлñя îñнîâнîй рàñòâîр KNO 3 êàê ÷иñòый, òàê и ñмåшàнный ñ дîпîлниòåльным рàñòâîрîм NaCl â прîпîрции 1:1. Выáîр дàнныõ âåщåñòâ îáóñлîâлåн пîяâлåниåм мîщныõ дîпîлниòåльныõ пиêîâ нà ñпåêòрå îñнîâнîгî рàñòâîрà â îáлàñòи îò 500 ñм-1 дî 1500 ñм-1 , ñâяçàнныõ ñ âàлåнòными êîлåáàниями àниîнà NO 3 и îòñóòñòâиåм пîлîñ â эòîй îáлàñòи ó дîпîлниòåльнîгî рàñòâîрà. В êà-÷åñòâå рàñòâîриòåля иñпîльçîâàлàñь диñòиллирîâàннàя âîдà. Схема эксперимента В дàннîй рàáîòå âñå ñпåêòры êîмáинàциîннîгî рàññåяния ñâåòà áыли пîлó÷åны при иñпîльçîâàнии мîдåрниçирîâàннîгî ñпåêòрîмåòрà ДФС-24 фирмы ЛÎÌÎ. Нåñмîòря нà нåêîòîрыå нåдîñòàòêи, îн îáлàдàåò êà÷åñòâåннîй îпòи÷åñêîй ÷àñòью и, ñîîòâåòñòâåннî, âыñîêим рàçрåшåниåм, нå óñòóпàющим ñîâрåмåн