摘要:

The heats and temperatures of transitions were measured for five pure compounds which were known or expected to form mesophases or liquid crystals. The five compounds were N-(p-cyanobenzal)-p-anisidine,p-(4-cyanobenzalamino)-cinnamic acid-active amyl ester, N, N'-tereph-thalylidene-di-p-toluidine,p-acetoxy-cinnamic acid, andp-[N-(p-methoxy-benzylidine)-amino]-phenyl acetate. Temperatures of transition for the compounds are reported here for the first time using a well-calibrated differential thermal analyzer. Heats of transitions for the compounds have not been previously reported. They were measured here by differential scanning calorimetry.

ISSN:0369-1152    

DOI:10.1080/15421406808083447

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Five aromatic hydrocarbon-TCNE complexes are dispersed in sodium chloride pellets and subjected to high pressures (0–25 kbar). The charge transfer absorption is enhanced and displaced toward lower energies at the highest pressure. An exception is the crystalline complex HMB-TCNE which exhibits a blue shift at the highest pressure. The doublet structure in both charge transfer bands of naphthalene-TCNE can be observed at 1 atm and at higher pressures. The importance of the relative sizes of donor and acceptor in environmental interactions are discussed.

ISSN:0369-1152    

DOI:10.1080/15421406808083448

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The polymorphism of crystalline cyclooctanone and cyclononanone has been investigated using X-ray diffraction, nuclear magnetic resonance spectroscopy and differential thermal analysis. Both compounds undergo phase transitions below room temperature; the crystalline phases stable at room temperature are highly disordered and are isostructural with corresponding phases of several widely differing compounds, including cyclooctane, cycloheptatriene, β-fluorine and γ-oxygen.

ISSN:0369-1152    

DOI:10.1080/15421406808083449

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Measurements of space-charge limited currents have been made on evaporated thin films of organic compoundp-quaterphenyl using metal electrodes. A study of current as a function of voltage and temperature indicated in layers examined the existence of an exponential trap level distribution. The new technique for evaluating the shape of trap level distribution was proposed.

ISSN:0369-1152    

DOI:10.1080/15421406808083450

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

This paper examines the difference between the ionization energies of various organic molecules both in the vapour and in various crystal lattices. Photoelectric emission thresholds of organic crystals, as well as being of intrinsic interest, provide information on the energies of the ionization energy of a molecule in the gas (IG) and in a molecular crystal (Ic) measures1the calculable polarization energyPof the crystal, a key quantity in the donor-acceptor theory of organic semiconductors.

ISSN:0369-1152    

DOI:10.1080/15421406808083451

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Components of the mobility tensor for electron and hole have been calculated in the tight binding approximation for 95°K and 290°K in anthracene crystal. The results for the temperature dependence of mobilities are in fair agreement with experiment. It follows from the performed calculations that, considering exchange effects, the application of the Hartree-Fock wave functions instead of those of the STO's (and possibly the potential of neutral hydrogens) should give good agreement with experiment for the anisotropy of the mobilities in both crystallographic planes.

ISSN:0369-1152    

DOI:10.1080/15421406808083452

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Two processes for photogeneration of carriers in Anthracene crystals, which have been proposed, among others, are the interaction of two singlet excitons created by light, and the ionization of one singlet or triplet exciton by absorption of a photon. Their relative importance is still controversial.

ISSN:0369-1152    

DOI:10.1080/15421406808083453

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Molecular crystals in general are receiving increased attention and anthracene crystals in particular are in demand for use in various studies. Consequently, several techniques have been developed for growing anthracene crystals–most of which have involved growth from the melt.1–3In those common method is to use a cooled collector plate.3,4The principal disadvantage of the latter method is the limited thickness of the crystal that can be obtained, owing to the low thermal conductivity of anthracene. In connection with our various studies of the interaction of energy with anthracene it is often necessary to be able to grow large and uniformly doped crystals. The techniques referred to above are not suited to the task. A procedure for growing relatively large anthracene crystals with tetracene uniformly distributed throughout is reported here.

ISSN:0369-1152    

DOI:10.1080/15421406808083454

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Calculations of singlet exciton states of the molecular crystals naphthalene and anthracene have been performed by Craig and Walsh,1Craig and Hobbins,2and more recently by Silbey, Jortner, Vala and Rice3and Silbey, Jortner and Rice.4Theoretical treatments follow the orignial work of Davydov for the interaction of a molecule and the weak crystal field. Since intermolecular overlap in a molecular crystal is small, the interaction between molecules may be represented as a multipole expansion. For an intense transition (f> 1.0) the Craig method retains only dipole terms in the expansion. These dipole sums are evaluated by the Ewald Kornfeld procedure or by direct summation over a sphere of 20–30 Å. Silbeyet al., however, compute the intermolecular interactions to 55 Å using π-electron wavefunctions or dipole summation, and beyond 55 Å using dipole sums. The main differences in the results of the treatments are due to the contributions of these long range interactions.

ISSN:0369-1152    

DOI:10.1080/15421406808083455

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor