Cooling quasiparticles in A(3)C(60) fullerides by excitonic mid-infrared absorption

Long after its discovery, superconductivity in alkali fullerides A(3)C(60) still challenges conventional wisdom. The freshest inroad in such ever-surprising physics is the behaviour under intense infrared excitation. Signatures attributable to a transient superconducting state extending up to temperatures ten times higher than the equilibrium T-c similar to 20 K have been discovered in K3C60 after ultra-short pulsed infrared irradiation-an effect which still appears as remarkable as mysterious. Motivated by the observation that the phenomenon is observed in a broad pumping frequency range that coincides with the mid-infrared electronic absorption peak still of unclear origin, rather than to transverse optical phonons as has been proposed, we advance here a radically new mechanism. First, we argue that this broad absorption peak represents a 'super-exciton' involving the promotion of one electron from the t(1u) half-filled state to a higher-energy empty t(1g) state, dramatically lowered in energy by the large dipole-dipole interaction acting in conjunction with the Jahn-Teller effect within the enormously degenerate manifold of (t(1u))(2)(t(1g))(1) states. Both long-lived and entropy-rich because they are triplets, the infrared-induced excitons act as a sort of cooling mechanism that permits transient superconductive signals to persist up to much higher temperatures

Radiation and cloud studies with GOME in preparation for future spectrometer missions

GOME is presently the only space-borne spectrometer observing the entire spectral range from 240 to 790 nm with high spectral resolution. Its data are an important source of information to prepare for the analysis of data from the new satellite spectrometers SCIAMACHY, OMI, and GOME-2. We present some examples of the use of GOME data for checking radiometric calibration and for multispectral studies of clouds. Regarding cloud studies with SCIAMACHY, the oxygen A-band around 761 nm can be used for retrieval of cloud fraction and cloud top pressure, and the range 1600-1750 nm can be used for discrimination of water and ice clouds

De effecten van aerosolen op de kortgolvige stralingsbalans

IPPC reports the aerosol radiative forcing per major aerosol category, like sulphate and fossil fuel derived carbon. Part of this carbon is reflective and part of the material (black carbon "soot") absorbs radiation. We find that in the Netherlands sulphate contributes some 30% to the reflection. Nitrate contributes even more; an estimated 35%. The local importance of nitrate is acknowledged in the new IPCC-TAR, but it is stated that insufficient data exist to assess its importance outside of the Netherlands. The amount of "fossil fuel" carbon could not be directly quantified. The reason is that it consists of thousands of different chemical compounds that all have different physicochemical properties. However, by deduction we found that its concentration is substantial. The mentioned three components, nitrate, sulphate and carbon, are thus the dominant aerosol components in the regional aerosol radiative forcing. As can be seen in the results, the forcing on partly cloudy days seems less because of a shorter sunshine duration. It should then be considered that on cloudy days the reflective power of the aerosol is higher due to the higher relative humidity and the associated uptake of water by the aerosol. This compensates for the shorter sunshine duration. Reflection of solar radiation caused by the aerosol is exerted by aerosol components that can be of a natural origin or produced by man. In our report we show, on the basis of the aerosol composition, that at least 85% of the aerosol is of a manmade origin and the aerosol reflection is therefore a forcing. The forcing is defined as the amount of solar radiation reflected back into space, and not available for heating of the earth due to the presence of manmade aerosol.SG-NO

The 2005 and 2006 DANDELIONS NO2 and aerosol intercomparison campaigns

Dutch Aerosol and Nitrogen Dioxide Experiments for Validation of OMI and SCIAMACHY (DANDELIONS) is a project that encompasses validation of spaceborne measurements of NO\u3csub\u3e2\u3c/sub\u3e by the Ozone Monitoring Instrument (OMI) and Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), and of aerosol by OMI and Advanced Along-Track Scanning Radiometer (AATSR), using an extensive set of ground-based and balloon measurements over the polluted area of the Netherlands. We present an extensive data set of ground-based, balloon, and satellite data on NO\u3csub\u3e2\u3c/sub\u3e, aerosols, and ozone obtained from two campaigns within the project, held during May-June 2005 and September 2006. We have used these data for first validation of OMI NO\u3csub\u3e2\u3c/sub\u3e, and the data are available through the Aura Validation Data Center website for use in other validation efforts. In this paper we describe the available data, and the methods and instruments used, including the National Institute of Public Health and the Environment (RIVM) NO\u3csub\u3e2\u3c/sub\u3e lidar. We show that NO\u3csub\u3e2\u3c/sub\u3e from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) compares well with in situ measurements. We show that different MAX-DOAS instruments, operating simultaneously during the campaign, give very similar results. We also provide unique information on the spatial homogeneity and the vertical and temporal variability of NO\u3csub\u3e2\u3c/sub\u3e, showing that during a number of days, the NO\u3csub\u3e2\u3c/sub\u3e columns derived from measurements in different directions varied significantly, which implies that, under polluted conditions, measurements in one single azimuth direction are not always representative for the averaged field that the satellite observes. In addition, we show that there is good agreement between tropospheric NO\u3csub\u3e2\u3c/sub\u3e from OMI and MAX-DOAS, and also between total NO\u3csub\u3e2\u3c/sub\u3e from OMI and direct-sun observations. Observations of the aerosol optical thickness (AOT) show that values derived with three ground-based instruments correspond well with each other, and with aerosol optical thicknesses observed by OMI. Copyright 2008 by the American Geophysical Union. U7 - Export Date: 2 August 2010 U7 - Source: Scopus U7 - Art. No.: D16S4