Use of laser-produced soft x rays for the production of excited metastable ions
TL;DR: In this article, a detailed investigation is presented of the use of soft x rays, emitted from a laser-produced plasma, for the excitation of highly energetic ions, and the effect of varying parameters such as laser energy, distance from the target, Li density, and time delay after the initial excitation has been examined.
Abstract: A detailed investigation is presented of the use of soft x rays, emitted from a laser-produced plasma, for the excitation of highly energetic ions The emphasis is on the excitation of ${\mathrm{Li}}^{+}(1s2s)$ metastable levels with energies of approximately 60 eV The experiments were made possible by the use of a geometry in which the laser beam was focused through the Li vapor onto a massive target placed inside the vapor Populations of ${\mathrm{Li}}^{+}(1s2s)$ ions in excess of ${10}^{15}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ have been measured and the effect of varying parameters such as laser energy, distance from the target, Li density, and time delay after the initial excitation has been examined In this work the plasma emission can be considered as radiation from a blackbody with a temperature of 10-100 eV, and the conversion efficiency from 106-\ensuremath{\mu}m radiation to blackbody radiation was estimated to be in excess of 5% A comparison has been made of the effect of using $Q$-switched ($\ensuremath{\tau}\ensuremath{\sim}10$ ns, $E\ensuremath{\sim}200$ mJ) and actively modelocked ($\ensuremath{\tau}\ensuremath{\sim}06$ ns, $E\ensuremath{\sim}50$ mJ) neodymium-doped yttrium aluminum garnet (Nd: YAG) lasers to make the soft-x-ray---emitting plasma ${\mathrm{Li}}^{+}(1s2s)$ population measurements have been made for the cases of Ta, Fe, Ni, and Li target materials, and the populations excited by photoelectrons into the $\mathrm{Li}(1{s}^{2}2p)$ and ${\mathrm{Li}}^{+}(1{s}^{2})$ levels have been measured The applications of these experiments to various proposed extreme-ultraviolet laser systems are discussed
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TL;DR: In this article, a review of the properties and applications of core-excited metastable atoms is presented, including the application of these atoms to several new types of spectroscopy that allow autoionizing linewidths as narrow as 0.1 cm−1 to be measured.
Abstract: The paper reviews both the properties and the applications of core-excited metastable atoms. The production of these atoms by microwaves, pulsed hollow-cathode discharges, and laser-produced x rays is described. We discuss the application of these atoms to several new types of spectroscopy that allow autoionizing linewidths as narrow as 0.1 cm−1 to be measured. The application of these metastables to the generation of picosecond-time-scale soft-x-ray pulses and to XUV lasers is also discussed.
27 citations
TL;DR: CsF vapor generated in a heat pipe was excited by a laser-produced plasma and time-resolved fluorescence on the ionic excimer transition Cs(2+)F(-) ?
Abstract: CsF vapor generated in a heat pipe was excited by a laser-produced plasma. Temporally integrated spectra and time-resolved fluorescence on the ionic excimer transition Cs(2+)F(-) ? Cs(+)F were observed at 185 nm. The pressure dependence of the fluorescence is influenced by self-absorption in the CsF vapor. The fluorescence is assigned to the Cs(2+)F(-) ((2)Sigma(1/2), B)? Cs(+)F ((2)Sigma(1/2),X) transition.
23 citations
TL;DR: A system is proposed whereby Zn atoms that are photoionized by soft x rays from a laser-produced plasma undergo selective super-Coster-Kronig decay leading to inversion and lasing on several XUV Zn III transitions.
Abstract: A system is proposed whereby Zn atoms that are photoionized by soft x rays from a laser-produced plasma undergo selective super-Coster–Kronig decay leading to inversion and lasing on several XUV Zn iii transitions. Calculations indicate that lasing will occur when a moderate-sized (∼10-J) 1.06-μm pump laser is used.
16 citations
TL;DR: In this article, the anti-Stokes Raman laser schemes in atomic sulphur and selenium are studied, allowing conversion of laser lines out of the 350- 178 nm range into the 200-130 nm range.
Abstract: Anti-Stokes Raman laser schemes in atomic sulphur and selenium are studied, allowing conversion of laser lines out of the 350- 178 nm range into the 200-130 nm range. The necessary population inversion with respect to the atomic metastable1S 0 levels is produced by photodissociation of the molecules COS and COSe with F 2 and ArF laser radiation, respectively. Anti-Stokes laser radiation at 167.5 and 158.7 nm for Se and at 182.0, 148.7, and 148.3 nm for S has been generated. Threshold pump energies of 0.1-20 μJ and output energies up to 5 μJ have been observed. At present, the systems are operated at low pump energies, just above threshold. It is expected that by the use of much higher pump energies and by further improvement of system parameters, output energies in the mJ range at MW peak powers will be possible for the VUV transitions.
15 citations
TL;DR: In this article, a continuous anti-Stokes-Raman (ASRL) oscillation between the 3d/sup 2/P and 4s/sup 1/P levels of the argon-ion laser plasma is described.
Abstract: Generation of continuous anti-Stokes-Raman laser (ASRL) oscillation between the 3d/sup 2/P and 4s/sup 2/P levels of the argon-ion laser plasma is described. Pump radiation of 648.3 nm (610.3 nm) is up-converted into 437.5-nm radiation with an overall efficiency of more than 20% and an output power of up to 150 mW. Thus far, a detuning of +or-9 GHz around the 4p/sup 2/S intermediate resonance was achieved. The experiments reported have demonstrated that the gain on a normal laser transition may be strongly increased by population transfer and due to coherent processes. Therefore the ASRL technique in general also demonstrates a possibility to overcome the problem of insufficient mirror reflectivities in the vacuum ultraviolet (VUV) region. >
15 citations
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TL;DR: The heat pipe oven as mentioned in this paper is a well-defined metal vapor device that continuously generates homogeneous vapors of well defined temperature, pressure, and optical path length, which can be used to control the temperature and pressure.
Abstract: A new, well‐defined metal vapor device called the heat‐pipe oven has been developed on the basis of the heat pipe, a heat conductive element designed by Grover and his co‐workers in Los Alamos. It continuously generates homogeneous vapors of well‐defined temperature, pressure, and optical path length. The vapor is confined by inert gas boundaries which remove the window problem and allow a direct pressure measurement without relying on vapor pressure curves. Due to the continuous evaporation and condensation the vapor purifies itself during operation.
308 citations
TL;DR: In this paper, the ejection of electrons from inner shells of atoms through photoionization is suggested as a straightforward means of creating population inversions at vacuum uv and x-ray wavelengths.
Abstract: The ejection of electrons from inner shells of atoms through photoionization is suggested as a straightforward means of creating population inversions at vacuum uv and x‐ray wavelengths. This can be accomplished by photon sources covering broad bands. Sodium vapor and solid copper are examined as possible candidates for laser action at 372 A and 1.54 A, respectively. A first‐rise traveling wave pump must be used; pumping powers required for superradiant operation run into several gigawatts, with rise times ranging from 10−9 sec in the near‐vacuum uv to 10−15 sec in the x‐ray region.
179 citations
TL;DR: The absolute cross section for ionization by electron impact has been measured for lithium, sodium, potassium, rubidium, and cesium by a modulated-crossed-beam technique as mentioned in this paper.
Abstract: The absolute cross section for ionization by electron impact has been measured for lithium, sodium, potassium, rubidium, and cesium by a modulated-crossed-beam technique. The measurement for lithium is described in detail, inasmuch as it has never been previously measured. The cross sections for the other alkali metals are included and compared with prior measurements for reference.
167 citations
TL;DR: The Hartree-Fock-Slater approach is used in this article to approximate the radial Schrodinger equation with a series of straight lines. But the Hartree Fock-slater equation is exactly solvable with Whittaker functions.
Abstract: The quantity $\ensuremath{-}\mathcal{r}(V(\mathcal{r})$ calculated by Herman and Skillman, using the Hartree-Fock-Slater approach, is approximated by a series of straight lines. With such a potential the radial Schr\"odinger equation is exactly solvable with Whittaker functions. The bound-state eigenvalue equation is found and is used to adjust the parameters of the straight lines so that the model eigenvalues and those of Herman and Skillman are in reasonable agreement. With the discrete and continuum orbitals of the model, the photo-ionization cross section for all the shells of the elements helium-xenon are computed.
164 citations
TL;DR: In this article, the x-ray emission of gold disks has been irradiated with 1.06 μm laser light at intensities between 7 × 1013 and 3 × 1015 W/cm2, and pulse lengths between 200 and 1000 psec.
Abstract: Gold disks have been irradiated with 1.06 μm laser light at intensities between 7 × 1013 and 3 × 1015 W/cm2, and pulse lengths between 200 and 1000 psec. Due to the high Z and long pulse, inverse bremsstrahlung becomes an important absorption mechanism and competes strongly with resonance absorption and stimulated scattering. In addition to measured absorptions, data on the temporal, spatial, angular, and spectral characteristics of the x‐ray emission are presented. Temporally and spectrally resolved back‐reflected light, and polarization‐dependent sidescattered light are detected, providing estimates for the amount of stimulated scattering and of the coronal electron temperature. Inhibited electron thermal conduction and nonlocal thermodynamic equilibrium ionization physics play key roles in bringing numerical simulations of these experiments into agreement with all of the above‐mentioned data.
119 citations