84 research outputs found
PURE EXCITION EMISSION FROM BENZENE CRYSTALS
No full textAuthor Institution: Department of Chemistry, Yale UniversityA computer based photon counting technique has enabled temperature dependent fluorescence measurements to be made in an accurate manner on the state of crystalline Benzene. The temperature range investigated was to . The fluorescence line shape that was studied was from the (0,0)---^{\prime\prime} transition. The density of states curve that these experiments yielded agreed in principle with that calcuiated by Colson. However, an improvement in the values chosen for the resonance exchange integrals was obtained. The results of this work leave no doubt that pure exciton emission from a molecular crystal can be seen and that there exists for the case of the state of Benzene a theory which can satisfactorily explain the temperature dependence of that emission’s line shape
TRIPLET ENERGY TRANSFER IN MIXED CRYSTALS OF BENZENE
No full textAuthor Institution: Sterling Chemistry Laboratory, Yale UniversityThe dependence of intensity ratios for peaks corresponding to orientationally distinct molecules in mixed crystals of isotopic benzenes is determined. A significant deviation from the statistical limit is observed as the trap concentration varies over the range 0 to 1\%. Three systems are studied; in , - in , and in sym-. The infinite dilution limit does not necessarily equal the statistical limit for occurence of the two traps. The variation in the intensity ratio with concentration can be explained in terms of energy transfer. The variation of the infinite-dilution intensity ratio from system to system is expected in light of an observed orientational effect on the lifetime
Credere senza dogma
No full textIn this chapter, the author looks for a form of belief without any dogmaticism
EXCITON BAND OF A ONE MOLECULE-PER-CELL CRYSTAL: HEXAMETHYLBENZENE
No full text S.D. Colson, D.M. Hanson, R. Kopelman and G. W. Robinson, J. Chem. Phys. 48, 2215 (1968).""Author Institution: Department of Chemistry, University of MichiganTwo methods for the determination of exciton structure are employed for this system (which cannot exhibit a Davydov splitting): The band-to-band (“hot band”) transition , and the heavily doped isotopic mixed crystal method. The experiments involve single crystals at low temperature ) and medium high resolution (. Results will be discussed in terms of translationally equivalent exciton interactions and effective one-dimensional energy transfer
RESOLVED EMISSION FROM COMPOUND STATES IN CHEMICALLY MIXED CRYSTALS
No full textAuthor Institution: Sterling Chemistry Laboratory, Yale UniversityThe emission spectrum of certain mixed crystals can be used to resolve the misting of compound states and measure the relative weighting of individual molecular This will be true when the electronic state inter-molecular mixing is large compared to that for the ground state vibrational levels of the two molecules. It must be further assumed that the vibronic intensity pattern for each molecule can be determined in a separate experiment. The system chosen to demonstrate this method is the p-dichlorobenzene-p-dibromobenzene (DCB-DBB) mixed crystal. This is an ideal system because the triplet states of DCB and DBB are nearly degenerate, their phosphorescence spectra have been studied in detail, and they are thought to form solid solutions at all concentrations. Furthermore, the ground state vibrational levels that are active in their respective spectra are significantly different in frequency. In conclusion, the emission spectrum of mixed crystals is found to show the effects of weak electronic state mixing and can be used to measure the extent of this mixing
Synthesis and characterisation of nanostructured BiFeO3 for photodecolourisation of azo dyes using visible light
Get PDFIn this work, effort is being made to synthesize a narrow band gap ferroelectric perovskite nanostructure semiconductor that is BiFeO3 (BFO). The BFO nanopowders were synthesized at 650ºC using a self-combustion method with glycine as the fuel. The effect of the different fuel concentrations, annealing temperatures and the duration of annealing are all demonstrated to influence the phase and crystallography of the synthesized nanoparticles. The author has demonstrated that the self-combustion process can be used to produce high purity BFO nanopowders which exhibit good absorption in the visible-light regime as determined by the UV-Vis-NIR spectroscopy with a measured optical band gap of 2.22 eV. Cont/d
The literary phenomenon of 'conflation’ in the reworking of Paul’s letter to the Colossians by the author of the letter to the Ephesians
Get PDFThis thesis is concerned with the nature of the relationship of the Letter to the Ephesians (Eph) to Paul's Letter to the Colossians (Col).The first three chapters seek to argue that this relationship should be designated as "literary dependent". In Chapter I the suggestion made by A.T. Lincoln (Dallas [Texas], 1990) that the contemporary redaction of the Letter of Aristeas by Josephus in his Jewish Antiquities, Book XII, §§ 11-118 is similar to the use the author of Eph made of Col, is exposed to critical review. Chapter II focuses on the phenomenon of repeated 'conflation' in Eph. This literary phenomenon entails that several 'Colossian' texts from different parts of Col are conflated by the author of Eph into one passage and is subjected to exhaustive analysis. It is argued that conflation is the main feature of the literary dependence of Eph on Col but does not occur in Josephus' reworking of the Letter of Aristeas. Chapter III continues the comparison between the method of reworking employed in the Jewish Antiquities and in Eph by pointing out that the fluctuation in verbatim agreement of one document with its source can be meaningful. Chapter IV provides the new synopsis of both letters on which the whole examination is based. This synoptic overview is a desideratum since the previous synoptic editions of the Greek text of both letters by E.J. Goodspeed (Chicago, 1933) and C.L. Mitton (Oxford, 1951) are not accurate enough and unsuitable for research that focuses on the conflations of 'Colossian' verses in Eph. The fifth and last chapter deals with the question why Eph is literary dependent on Col and shows that despite the literary dependence, the theology of Eph is distinctive in comparison with its source Col. The distinctiveness of Eph's theology consists in a critical modification of the stress which Col places on Christ's already accomplished victory over the cosmic powers (Co/ 2.15). In order to safeguard an authoritative reception of his modification of Col, the author of Eph presented his letter as the parallel letter of Col alluded to m Col 4.16. The literary dependence on Col is necessary both to modify its content and to present his own writing as its parallel letter
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