Frenkel and charge transfer excitons in C60

We have studied the low energy electronic excitations of C60 using momentum dependent electron energy-loss spectroscopy in transmission. The momentum dependent intensity of the gap excitation allows the first direct experimental determination of the energy of the 1Hg excitation and thus also of the total width of the multiplet resulting from the gap transition. In addition, we could elucidate the nature of the following excitations - as either Frenkel or charge transfer excitons.Comment: RevTEX, 3 Figures, to appear in Phys. Rev.

Electronic polarization in pentacene crystals and thin films

Electronic polarization is evaluated in pentacene crystals and in thin films on a metallic substrate using a self-consistent method for computing charge redistribution in non-overlapping molecules. The optical dielectric constant and its principal axes are reported for a neutral crystal. The polarization energies P+ and P- of a cation and anion at infinite separation are found for both molecules in the crystal's unit cell in the bulk, at the surface, and at the organic-metal interface of a film of N molecular layers. We find that a single pentacene layer with herring-bone packing provides a screening environment approaching the bulk. The polarization contribution to the transport gap P=(P+)+(P-), which is 2.01 eV in the bulk, decreases and increases by only ~ 10% at surfaces and interfaces, respectively. We also compute the polarization energy of charge-transfer (CT) states with fixed separation between anion and cation, and compare to electroabsorption data and to submolecular calculations. Electronic polarization of ~ 1 eV per charge has a major role for transport in organic molecular systems with limited overlap.Comment: 10 revtex pages, 6 PS figures embedde

Long-range corrected DFT calculations of charge-transfer integrals in model metal-free phthalocyanine complexes

An assessment of several widely used exchange--correlation potentials in computing charge-transfer integrals is performed. In particular, we employ the recently proposed Coulomb-attenuated model which was proven by other authors to improve upon conventional functionals in the case of charge-transfer excitations. For further validation, two distinct approaches to compute the property in question are compared for a phthalocyanine dimer

Reduced costs with bisoprolol treatment for heart failure - An economic analysis of the second Cardiac Insufficiency Bisoprolol Study (CIBIS-II)

Background Beta-blockers, used as an adjunctive to diuretics, digoxin and angiotensin converting enzyme inhibitors, improve survival in chronic heart failure. We report a prospectively planned economic analysis of the cost of adjunctive beta-blocker therapy in the second Cardiac Insufficiency BIsoprolol Study (CIBIS II). Methods Resource utilization data (drug therapy, number of hospital admissions, length of hospital stay, ward type) were collected prospectively in all patients in CIBIS . These data were used to determine the additional direct costs incurred, and savings made, with bisoprolol therapy. As well as the cost of the drug, additional costs related to bisoprolol therapy were added to cover the supervision of treatment initiation and titration (four outpatient clinic/office visits). Per them (hospital bed day) costings were carried out for France, Germany and the U.K. Diagnosis related group costings were performed for France and the U.K. Our analyses took the perspective of a third party payer in France and Germany and the National Health Service in the U.K. Results Overall, fewer patients were hospitalized in the bisoprolol group, there were fewer hospital admissions perpatient hospitalized, fewer hospital admissions overall, fewer days spent in hospital and fewer days spent in the most expensive type of ward. As a consequence the cost of care in the bisoprolol group was 5-10% less in all three countries, in the per them analysis, even taking into account the cost of bisoprolol and the extra initiation/up-titration visits. The cost per patient treated in the placebo and bisoprolol groups was FF35 009 vs FF31 762 in France, DM11 563 vs DM10 784 in Germany and pound 4987 vs pound 4722 in the U.K. The diagnosis related group analysis gave similar results. Interpretation Not only did bisoprolol increase survival and reduce hospital admissions in CIBIS II, it also cut the cost of care in so doing. This `win-win' situation of positive health benefits associated with cost savings is Favourable from the point of view of both the patient and health care systems. These findings add further support for the use of beta-blockers in chronic heart failure

Exciton Electro-Absorption at Non-Zero Wave Vector

Based on a previously proposed two-dimensional model of a polyacene crystal, the contributions to the electro-absorption signal from different points of the exciton Brillouin zone are calculated. They are shown to differ substantially both in amplitude and in shape. This makes electro-absorption spectra very sensitive to vibronic coupling. On the one hand, the new factor is a potential complication in theoretical interpretations. On the other hand, it favours electro-absorption spectroscopy as a promising experimental tool to study vibronic effects

Cluster Model of Charge Transfer Excitons in Molecular Crystals. I. Neat Crystals

A two-dimensional finite cluster model is proposed to describe the coupling of low energy charge transfer and Frenkel states of an anthracene-like molecular crystal. The results confirm most of the qualitative conclusions of the extensively used linear crystal model, but suggest the necessity to review some of its quantitative results. Potential usefulness of the cluster model for the description of doped crystals is pointed out

Thermoluminescence dosimetry of liquid 32P sources of variable size and composition

Dosimetry of liquid sources was studied in terms of their size and composition, to check how self-absorption of balloon-based intravascular brachytherapy sources may influence doses at a target point.The sources contained aqueous solutions of -phosphate, saline, and iodinated contrast media (0–). Doses were measured in Plexiglas phantoms at radial distance, using miniature flat thermoluminescence detectors.The absolute dose rates measured for 2.0– diameter range increased from 0.25 to 0.43 and were slightly lower than theoretical values. A diameter balloon delivered 0.33, and a ID Plexiglas tube 0.40 . A titanium stent present on the balloon enhanced the dose rate at distance, whereas an one reduced it. The influence of iodine concentration was not very well pronounced.The observed increase of absolute dose rates in the clinically essential range of source diameters is an important parameter for radiotherapy planning