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We present the status of optical field ionization soft X-ray lasers. The amplifying medium is generated by focusing a high-energy circularly polarized 30-fs 10-Hz Ti: sapphire laser system in a gaseous medium. Using xenon or krypton, strong laser emission at 41.8 and 32.8 nm, respectively, has been observed. After presenting the basis of the physics, we present recent characterization of the sources as well as dramatic improvement of their performances using the waveguiding technique. [ABSTRACT FROM PUBLISHER]

Quantitative phase-sensitive measurements of ultrafast optical-field ionization rates in molecular H2, N2, and O2 are obtained using a temporally gated frequency-domain interferometric pulse measurement technique: multipulse interferometric frequency-resolved optical gating (MI-FROG). By measuring the pump-induced frequency change on a weak copropagating probe pulse, the optical field ionization dynamics can be completely time-resolved with sub-pulsewidth time resolution. A one-dimensional nonrelativistic electromagnetic fluid code model is used to compute the ionization dynamics and optical field propagation through the plasma. Using the Ammosov-Delone-Krainov (ADK) tunnel ionization rate model originally developed for atoms, the relatively simple model proposed here has been shown to compare favorably with the MI-FROG measured ionization rates in noble gases in the intermediate intensity regime (10 14 W/cm2) (Siders et al, Phys. Rev. Lett.). We attempt to unify our studies in noble gases and molecules by performing experiments on N2 and O2, which have nearly identical ionization potentials to Ar and Xe, respectively. For the molecules studied here, we show that an ADK-like description of molecular ionization rates calculated from the model agree with the experimentally measured rates using the MI-FROG technique for H2 and N2. In the case of O2, however, the experimentally measured ionization rate is approximately two orders of magnitude lower than that expected from the standard ADK formula. This is in agreement with the previously observed suppressed O2 ionization rate in ion mass spectroscopy studies (Guo, 2000). We attribute the suppressed ionization rate in O2 to a multielectron screening effect and show that a modified version of the ADK formula, taking into account the electron screening as proposed by Guo, well approximates the MI-FROG O2 ionization rate data [ABSTRACT FROM PUBLISHER]

Summarize the unique properties of the Cd atom that have lead to many new types of laser excitation schemes and processes that began 35 years ago. These include the CW blue and ultraviolet laser transitions in Cd+, the generation of 125-ps pulses (the shortest mode-locked pulses at that time), the process of Penning ionization as a laser excitation mechanism, recombination lasers produced by both laser-produced plasmas and a new segmented arc recombination laser (SPER laser) and the first soft-X-ray pumped photoionization laser, which are all described briefly [ABSTRACT FROM PUBLISHER]

Recent studies on the laser photochemistry of aromatic and aliphatic amino acids and small peptides in neutral aqueous solution are described. We report on major parameters such as photoionization and photodecomposition quantum yields for the cases of direct (and indirect) photolysis. Although four different UV laser sources were used, the impact is made on 193-nm-induced photoprocesses. The relative probabilities of photochemical damage of specific residues are estimated. It is shown that the peptide bond is likely to be the main target in collagen. Its scission could be the most important photochemical reaction taking place at 193-nm laser irradiation of the cornea. We have found strong arguments in favor of the ablative photodecomposition mechanism of photorefractive keratectomy [ABSTRACT FROM PUBLISHER]