title: X rays from optical-field ionized plasmas at low density.
abstract: We present results of an experiment in which x rays from an optical-field ionized plasma are generated under well-controlled conditions in a low-pressure gas cell. In this way high-density effects such as electron heating, collisional ionization, and ionization defocusing are avoided. Using N(2) as the medium, we show that many features of the soft-x-ray emission follow theoretical predictions. In particular, higher x-ray intensity is observed on most lines for circularly than for linearly polarized light. However, several Li-like lines show anomalously strong emission for linear polarization. Mechanisms that may be responsible for this effect are discussed.
authors.affiliation: Max-Planck-Institut für Quantenoptik, D-85748 Garching, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Pretzler
authors.forename: E E
authors.initials: EE
authors.lastname: Fill