摘要:

The fluorescence spectra of coronene and 1,12-benzoperylene have been studied in frozen heptane as a function of pressure (0–30 kbar). The fluorescence red shifts at 77°K are 5 cm−1/kbar and 8.3 cm−1/kbar, respectively. High pressures broaden vibronic bands and increase background intensity. The 0, 0 band becomes more pronounced under pressure. The intensity pattern of the 1,12-benzoperylene fluorescence is altered considerably by compression of the heptane matrix. Permanent changes in the spectra after pressure treatment are very slight compared to the reversible effects of high pressures on the spectral characteristics of these two aromatic hydrocarbons.

ISSN:0369-1152    

DOI:10.1080/15421406908083457

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Secondary emission results show that the energy needed to create an electron-hole pair by low-energy electron bombardment of anthracene crystals is less than 75 eV, and that the thermalization distance of a secondary is such that initial recombination cannot account for the low yield of one pair per 400 eV obtained by Delany and Hirsch. It is suggested that columnar recombination accounts for at least part of the difference.

ISSN:0369-1152    

DOI:10.1080/15421406908083458

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

A study of the relationship between radical recombination kinetics, as determined by electron paramagnetic resonance annealing studies, and molecular motion in anthracene single crystals is presented. Although the initial stages of annealing are complicated by a number of effects, the latter stages clearly proceed by a diffusion controlled mechanism which is identical to bulk self-diffusion. From such kinetics, one can estimate self-diffusion coefficients at much lower temperatures than can be done by sectioning techniques.

ISSN:0369-1152    

DOI:10.1080/15421406908083459

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Eight mesophase-forming compounds were studied by the technique of depolarized light analysis. The temperatures at which anisotropy changes occurred were compared with results from differential thermal analysis. Although anisotropy change and uptake of heat are usually synchronous, in some cases thermal uptake is almost complete prior to a significant change in the anisotropic behavior of the compound. The observations made explain many of the discrepancies between mesophase transition temperatures observed by differential thermal analysis and optical methods. Photomicrographs of the various mesophase types examined are presented.

ISSN:0369-1152    

DOI:10.1080/15421406908083460

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Dark- and photo-current measurements are used to study trap characteristics and optical de-trapping processes in anthracene samples provided with alkali and alkaline-earth metal contacts. The spectral response of the photocurrent yield in the entire photon-energy range studied (0.95–3.4 eV) originates from optical excitation of electrons from a single discrete set of traps which is continuously filled by electron injection from the active metal contact. The traps are 0.95 eV deep and are present with a density of about 1013cm−3. De-trapping appears to occur by direct photoexcitation into the conduction band at long wavelengths and by interaction of occupied traps with triplet and singlet excitons at shorter wavelengths. The spectral yield curve exhibits considerable structure which can be advantageously used to study the various electronic-vibronic states in anthracene.

ISSN:0369-1152    

DOI:10.1080/15421406908083461

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

Single crystals of phenanthrene were found to exhibit a heat capacity anomaly and anomalous electrical effect in the vicinity of 72°C.1,2A heat capacity anomaly was also found in this material in powder form. As a result of calculations3and other measurements4it is quite possible that the source of the anomalous behavior of phenanthrene is the crowded hydrogen atoms at the 4,5 positions of the molecule. A calorimetric survey was made of some other hydrocarbons with crowded hydrogens in the hope of finding materials which exhibit similar behavior.

ISSN:0369-1152    

DOI:10.1080/15421406908083462

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

An optical method of detection of electron spin resonance of metastable states has permitted the investigation of the triplet entity responsible for the blue component in the phosphorescence of purified crystalline durene. This entity has fine structure parameters

ISSN:0369-1152    

DOI:10.1080/15421406908083463

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The polarized UV absorption spectrum of 9-cyanonanthracene crystal at 4.2°K is reported. The absorption polarization ratio for light polarized along thec- anda-axes is compatible with the assignment of the long wave system to a short axis transition as in the case of anthracene itself.

ISSN:0369-1152    

DOI:10.1080/15421406908083464

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

In a recent paper,1hereafter referred to as (1) Chojnacki has reported calculation of transfer integrals in anthracene crystal at both room and low temperature (290 °K, 95 °K). He uses Slater atomic wave functions with an exponent α = 3.08 Å−1, together with Hückel coefficients, in order to build the molecular wave function of the excess electron (or hole) on an anthracene molecule. The crystal structure at those two temperatures was studied by Mason2who showed that there was not only a change in the dimensions and the angle of the monoclinic unit cell but also slight rotation of the molecules within this unit cell.

ISSN:0369-1152    

DOI:10.1080/15421406908083465

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor

摘要:

The problem of the theoretical prediction of the temperature dependence of current carriers mobilities in molecular solids has been studied in general within the framework of the band theory for both narrow and broad band cases givingn< 2 in the relation m ∼T−nwhen only single acoustic phonon scattering processes are considered.6A possible role of the intermolecular resonance integrals (transfer integrals T.I.) for an explanation of the temperature dependence of mobilities in anthracene crystal has also been studied recently.3

ISSN:0369-1152    

DOI:10.1080/15421406908083466

出版商:Taylor & Francis Group    

年代:1969

数据来源: Taylor