Singlet molecular oxygen (a1Δg) is shown to be the principal reactive intermediate in the photoinduced oxygen-dependent decomposition of a series of phenylenevinylene oligomers. The reaction rate between singlet oxygen and the oligomer decreases (1) with a decrease in the extent of phenylenevinylene conjugation (i.e., oligomer chain length) and (2) upon the incorporation of electron-withdrawing substituents on the oligomer. The reaction rate, however, does not appear to depend solely on the electron density of the oligomer π system, as calculated using ab initio methods. For oligomers with vinyl-substituted cyano group(s), the reaction with singlet oxygen is very slow, thus making such compounds good candidates for the production of stable electroluminescent materials.

In a time-resolved infrared spectroscopic study, the a1Δg → b1Σg + absorption spectrum of molecular oxygen at ∼5200 cm-1 was recorded in 19 solvents using a step-scan Fourier transform infrared spectrometer. Solvent-dependent changes in the full width at half-maximum of this absorption band covered a range of ∼30 cm-1 and solvent-dependent changes in the position of the band maximum covered a range of ∼55 cm-1. When considered along with solvent-dependent O2(a1Δg) → O2(X3Σg -) emission data, the current results identify features that must be incorporated in computational models of the interaction between oxygen and the surrounding solvent. In particular, data presented herein clearly demonstrate the importance of considering the influence of equilibrium and nonequilibrium solvation when interpreting the effect of solvent on transitions between the X3Σg -, a1Δg, and b1Σg + states of oxygen. The data indicate that the bandwidths of the O2(a1Δg) → O2(b1Σg +) and O2(a1Δg) → O2(X3Σg -) transitions principally reflect the effects of equilibrium solvation, whereas the associated solvent-dependent spectral shifts reflect the effects of both equilibrium and nonequilibrium solvation. These general conclusions make it possible to resolve some long-standing problems associated with early attempts to interpret the effect of solvent on electronic transitions in oxygen

Thin films of the luminescent polymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) were deposited in high vacuum directly from toluene solution on Ag substrates using a homemade electrospray (ES) deposition system. The films were deposited in multiple steps without breaking the vacuum and characterized in situ using photoemission spectroscopy. The x-ray photoemission spectroscopy measurements indicate that the deposited layers are essentially contamination free and that subsequent depositions can be performed using the ES system without dissolving the previously deposited layers. Additional ultraviolet photoemission spectroscopy measurements showed the development of the highest occupied molecular-orbital structure as the MEH-PPV layer increased in thickness. This allowed the determination of the charge injection barriers (orbital alignment) at the Ag∕MEH-PPV interface.

Ribonucleic acid (RNA) homopolymer thin films on highly oriented pyrolytic graphite (HOPG) were prepared in ultrahigh vacuum (UHV) directly from aqueous solution by electrospray (ES) injection. The polyadenosine (poly rA) films were prepared in several steps of increasing thickness without breaking the vacuum. Before deposition and between deposition steps, the samples were characterized with photoemission spectroscopy (PES). Both X-ray and ultraviolet photoemission spectroscopy (XPS and UPS) were employed. XPS enabled the detailed measurement of core level peaks, giving insight into the chemical interaction at the interface and the layer morphology. The corresponding UP-spectra sequence allowed us to directly follow the transition from HOPG valence bands to the poly rA highest occupied molecular orbital (HOMO) structure. This enabled the determination of the poly rA ionization energy and work function as well as the charge injection barriers between the Fermi level of the HOPG substrate and the poly rA HOMO. The injection barrier between the lowest unoccupied molecular orbital (LUMO) and the HOPG Fermi level was determined using the HOMO-LUMO gap value determined by optical absorption. The results indicate that significant injection barriers exist between HOPG and the poly rA overlayer, limiting conductivity across this interface.

Dedicated to Professor Andre M. Braun on the occasion of his 60th birthday Experiments were performed in an attempt to identify the reactive intermediate(s) involved in the degradation of a polyamide, Nylon 66, in chlorinated water. According to previous studies, N-chlorination is certainly one reaction that ultimately contributes to polyamide degradation. In this case, the intermediates involved could either be Cl 2 or HClO. Available information also indicates that, for many polymers, singlet molecular oxygen (a 1 D g ), chemically generated from HClO, could likewise be involved as an intermediate in a degradation reaction. Thus, tests were undertaken to specifically address this latter issue with respect to polyamide degradation. The degradation of Nylon 66 was monitored under a variety of conditions by FT-IR spectroscopy. The rate of degradation was pH-dependent, and degradation was most pronounced at pH`5. Characteristic tests for the intermediacy of singlet oxygen, however, were negative. Rather, the data strongly pointed to Cl 2 as the key intermediate in the degradation. The presence of compounds capable of being oxidized by Cl 2 arrested the degradation reaction. These results should be pertinent in an attempt to stabilize polymers exposed, e.g., to water that has been chlorinated to kill bacteria (i.e., drinking water).Introduction. ± The use of Cl 2 as a disinfectant to kill bacteria and thus make water potable is well-established [1]. It is also acknowledged that many polymeric materials in contact with chlorinated water degrade at rates that can adversely influence the properties and, hence, function of the polymer [2 ± 4]. Purification membranes, pipes, and pump parts made from, e.g., polyamides, polyethylene, and polypropylene routinely show the effects of exposure to chlorinated water that, in turn, often requires replacement of these items at more frequent intervals. In the present context, degradation means any change at the molecular level that alters the properties of the polymer. Low levels of degradation can influence properties such as elasticity and permeability, whereas high levels of degradation can result in loss of material and the formation of sizable cracks in molded samples.To more accurately describe chlorinated water, it is necessary to specify the pH of the system and to consider the equilibrium of Eqn. 1.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. Terms of use: Documents in AbstractUsing only aggregate data as observables, we estimate multisector sticky-price models for twelve countries, allowing the degree of price stickiness to vary across sectors. We use a specification that allows us to extract information about the underlying crosssectional distribution from aggregate data. Identification is possible because sectors play different roles in determining the response of aggregate variables to shocks at different frequencies: sectors where prices are more sticky are relatively more important in determining the low-frequency response. We find that the inferred distributions of price stickiness conform quite well with empirical distributions constructed from the available microeconomic evidence on price setting. We then explore our Bayesian approach to combine the aggregate time-series data with the microeconomic information on the distributions of price rigidity, and re-estimate the models for the United States, Denmark, and Japan. Our results show that allowing for this type of heterogeneity is critically important to understanding the joint dynamics of output and prices, and it constitutes a step toward reconciling the extent of nominal price rigidity implied by aggregate data with the evidence from price micro data.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. The Working Papers of Danmarks Nationalbank describe research and development, often still ongoing, as a contribution to the professional debate. Terms of use: Documents inThe viewpoints and conclusions stated are the responsibility of the individual contributors, and do not necessarily reflect the views of Danmarks Nationalbank.As a general rule, Working Papers are not translated, but are available in the original language used by the contributor. Danmarks Nationalbank's Working Papers are published in PDF format at www.nationalbanken.dk. A free electronic subscription is also available at this Web site.The subscriber receives an e-mail notification whenever a new Working Paper is published.Please direct any enquiries to Danmarks Nationalbank, Communications, Havnegade 5, DK-1093 Copenhagen K Denmark E-mail: kommunikation@nationalbanken.dkText may be copied from this publication provided that Danmarks Nationalbank is specifically stated as the source. Changes to or misrepresentation of the content are not permitted.Nationalbankens Working Papers beskriver forsknings-og udviklingsarbejde, ofte af foreløbig karakter, med henblik på at bidrage til en faglig debat.Synspunkter og konklusioner står for forfatternes regning og er derfor ikke nødvendigvis udtryk for Nationalbankens holdninger.Working Papers vil som regel ikke blive oversat, men vil kun foreligge på det sprog, forfatterne har brugt.Danmarks Nationalbanks Working Papers er tilgaengelige på www.nationalbanken.dk i pdf-format. På hjemmesiden er det muligt at oprette et gratis elektronisk abonnement, der leverer en e-mail notifikation ved enhver udgivelse af et Working Paper.Henvendelser kan rettes til: Danmarks Nationalbank, Kommunikation, Havnegade 5, 1093 København K. E-mail: kommunikation@nationalbanken.dk Det er tilladt at kopiere fra Nationalbankens Working Papers forudsat, at Danmarks Nationalbank udtrykkeligt anføres som kilde. Det er ikke tilladt at aendre eller forvanske indholdet. ISSN (online) 1602-1193 REAL RIGIDITIES AND THE CROSS-SECTIONAL DISTRIBUTION OF PRICE STICKINESS: EVIDENCE FROM MICRO AND MACRO DATA COMBINEDContact for this working paper: Niels Arne Dam Danmarks Nationalbank nad@nationalbanken.dk RESUME Vi opstiller en standard-model med stive priser, som kan belyse relevansen af tre mekanismer, der potentielt kan forlige de forholdsvis hyppige prisaendringer i mikroøkonomiske data med de store og langvarige effekter af monetaere stød, som findes i analyser af makroøkonomiske t...

We provide evidence on three mechanisms that can reconcile frequent individual price changes with sluggish aggregate price dynamics. To that end, we estimate a semistructural model that can extract information about real rigidities and the distribution of price stickiness from aggregate data. Hence, the model can also speak to the debate about the aggregate implications of sales. Our estimates indicate large real rigidities and substantial heterogeneity in price stickiness. Moreover, the cross-sectional distribution of price stickiness implied by aggregate data is in line with an empirical distribution obtained from microprice data that factors out sales and product substitutions.