Atomic and molecular phases through attosecond streaking

In attosecond streaking, an electron is released by a short xuv pulse into a strong near infrared laser field. When the laser coupling between two states in the target is weak relative to the detuning, the streaking technique, which allows for a complete determination of the driving field, also gives an accurate measurement of the relative phase of the atomic or molecular ionization matrix elements from the two states through the interference from the two channels. The interference may change the phase of the photoelectron streaking signal within the envelope of the ir field, an effect to be accounted for when reconstructing short pulses from the photoelectron signal and in attosecond time-resolved measurements.Comment: 5 pages, 5 figure

The Growth Opportunities for SMEs?

The extensive empirical literature on the validity of Gibrat’s law does not in general verify the law as it finds that firms’ growth rates are negatively correlated with both firm size and age. However, some studies find that Gibrat’s law holds for sub-samples of firms such as large firms or firms belonging to special industries. It has been pointed out that these results are due to the fact that the likelihood of firm survival for natural reasons is positively related to firm size and age. This study uses a relatively large and representative sample of Danish firms to evaluate the validity of Gibrat’s law for different kinds of firms over the period 1990 - 2003. In contrast to the majority of earlier studies our analysis corrects for the bias in the estimations by using variables related to the survival of small firms.Market Structure; Firm Strategy; Market Performance;

Polarization effects in attosecond photoelectron spectroscopy

We study the influence of polarization effects in streaking by combined atto- and femtosecond pulses. The polarization-induced terms alter the streaking spectrum. The normal streaking spectrum, which maps to the vector potential of the femtosecond pulse, is modified by a contribution following the field instead. We show that polarization effects may lead to an apparent temporal shift, that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization effects will lead to an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s state in atomic hydrogen.Comment: 4 pages, 3 figure