Time-resolved photoelectron spectroscopy using synchrotron radiation time structure.

Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera-based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photoemitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station.

Reduction of beta-adrenergic receptors can explain the lack of rebound effect after tertatolol withdrawal.

Tertatolol is a potent beta-blocker with no intrinsic sympathomimetic activity (ISA) or beta 1/beta 2 receptor subtype selectivity. We provide evidence that tertatolol competitively inhibits beta-adrenergic receptors (beta-AR) and induces a marked and persistent reduction of their number. This has been consistently found in vitro and in vivo. The in vitro study showed that the receptor reduction by tertatolol was rapid (about 1 h at 37 degrees C), slowly reversible and independent of ISA. This effect was also observed in vivo. In healthy volunteers, seven days tertatolol treatment lowered the number of beta-AR by 26%. This number gradually rose back to the pretreatment levels, and a significant effect was still present on day 3 after drug withdrawal. The reduction of heart rate by tertatolol was also persistent and was still significant on day 3 to 5 after drug withdrawal. We conclude that the reduction of the receptor numbers may be important in producing a lack of a rebound effect after discontinuation of chronic tertatolol treatment.