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This paper, “A solid state Doppler wind lidar system on ISSa," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

To maintain mobility in patients with chronic hypoxemia who are under long-term oxygen therapy, portable oxygen systems are available. They have the disadvantage of a short range. To prolong the range and to reduce the cost of oxygen treatment, demand oxygen delivery systems (DODS) are used. Aim of the study was to compare three DODS (DOC-2000 [D], TransTracheal Inc.; Oxytron [O], Weinmann; Pulsair [P], DeVilbiss, Sunrise Medical) with continuous oxygen delivery. 17 patients (age 67.82 +/- 9.46 years; FEV1 1.23 +/- 0.69 l; PaO2 48.8 +/- 6.7 mm Hg) were studied. The continuous flow oxygen (CONT) and the DODS were applied to the patients for 30 minutes each in random sequence with an airflow of 2 l/min. After 15 and 30 minutes arterial blood gas analysis was done. Oxygen saturation was recorded continuously by pulseoximetry. After 15 minutes no significant differences in PaO2 were found between CONT and DODS. After 30 minutes no significant difference in PaO2 was found in CONT as compared to P. Significant lower PaO2 values were found for O and D as compared to CONT (p < 0.01). With P the range of a portable oxygen source was increased by 161.5 percent, with O by 172 percent, with D the range was increased by only 17.2 percent. Prolongation of range of a portable oxygen source can be achieved by means of DODS without a decrease of PaO2 and thus without loss of quality of the oxygen treatment. However, there are differences in efficacy between the DODS.

The hyperfine structure (hfs) of 12 metastable states of47Ti has been measured by laser induced fluorescence. 11 of these states have been measured additionally very precisely by a laser-rf double resonance method. Taking into account results of earlier hfs measurements, the hfs of altogether 17 fine structure states has been analyzed by the simultaneous parametrization of the one- and two-body interactions in the atomic hfs for the model space (3d+4s)N+2 (N=2). This gives 16 parameters for the magnetic dipole interaction and 12 parameters for the electric quadrupole interaction. From the model space parameters, obtained from the hfs fit, the nuclear quadrupole momentQ(47Ti)=0.303(24b), has been evaluated at the first time; it is free of Sternheimer corrections up to second order.

This study develops a heterodyne interferometer utilizing differential wavefront sensing for tilt measurement. The interferometer has sub-nm sensitivity in translation measurement and sub-μrad sensitivity in tilt measurement for the LISA (laser interferometer space antenna) inertial sensor. The interferometer design is based on maximum symmetry where reference and measurement arm have the same optical pathlength, frequency and polarization.

To maintain mobility in patients with chronic hypoxemia who are under long-term oxygen therapy, portable oxygen systems are available. They have the disadvantage of a short range. To prolong the range and to reduce the cost of oxygen treatment, demand oxygen delivery systems (DODS) are used. Aim of the study was to compare three DODS (DOC-2000 [D], TransTracheal Inc.; Oxytron [O], Weinmann; Pulsair [P], DeVilbiss, Sunrise Medical) with continuous oxygen delivery. 17 patients (age 67.82 +/- 9.46 years; FEV1 1.23 +/- 0.69 l; PaO2 48.8 +/- 6.7 mm Hg) were studied. The continuous flow oxygen (CONT) and the DODS were applied to the patients for 30 minutes each in random sequence with an airflow of 2 l/min. After 15 and 30 minutes arterial blood gas analysis was done. Oxygen saturation was recorded continuously by pulseoximetry. After 15 minutes no significant differences in PaO2 were found between CONT and DODS. After 30 minutes no significant difference in PaO2 was found in CONT as compared to P. Significant lower PaO2 values were found for O and D as compared to CONT (p0.01). With P the range of a portable oxygen source was increased by 161.5 percent, with O by 172 percent, with D the range was increased by only 17.2 percent. Prolongation of range of a portable oxygen source can be achieved by means of DODS without a decrease of PaO2 and thus without loss of quality of the oxygen treatment. However, there are differences in efficacy between the DODS.

Ambitious future space missions require extreme pointing accuracy and internal length stability, because they are based on optical/infrared interferometry. A technology precursor experiment is proposed, involving the German built ASTRO-SPAS, a space shuttle retrievable subsatellite. The objective of this experiment is the verification of key technologies and functions for an optical free-flyer interferometer, a laser gravitational wave detector (LISA) -both potential Horizon 2000plus cornerstone missions- and coherent inter-satellite laser communications (SOLACOS).

An experimental optical communications link between two stratospheric balloons is proposed as an intermediate step from limited ground laboratory tests to costly space operations. Such an experiment can overcome many environmental constraints encountered on the ground, and allows all measurements to be made directly in the antenna far field. Early performance demonstrations are possible which allow experimental trade-offs between alternative technologies and the verification of concepts, critical system parameters and subfunctions under near space conditions.

The hyperfine structure of the metastable atomic states (3d74s)5F2,3,4,5 and (3d 7 4s)3F2,3,4 of57Fe has been measured using theABMR- LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). From these measurements the following hfs constantsA of the magnetic dipole interaction have been obtained (corrected for second order effects):A(5F2)=55.994(7) MHzA(5F3)=69.632(5) MHzA(5F4)=78.435(4) MHzA(5F5)=87.246(3) MHzA(3F2)=143.328(4) MHzA(3F3)=50.602(10) MHzA(3F4)=13.456(5) MHz

A method of simultaneous parametrization of one- and two-body interactions in atomic hyperfine structure (HFS) of the configurations (3d+4s)N+2 is proposed. It is shown that the HFS of these configurations can be parametrized by the use of sixteen adjustable radial parameters for the magnetic dipole interaction and twelve radial parameters for the electric quadrupole interaction. From these one- and two-body parameters nuclear quadrupole moments can be evaluated which are almost free of Sternheimer corrections.

In our systematic investigations on the hyperfine structure (hfs) of high lying metastable states in 3d-shell atoms we have found evidence for an extraordinary strong far configuration mixing effect on off-diagonal matrix elements between configurations. Using theABMR-LIRF method the hfs of (3d 2 4s 2)3 P 47Ti, (3d 3 4s 2)4 P 51V (3d 5 4s 2)4 G 55Mn and (3d 6 4s 2)3 H 57Fe has been measured. Values found for the effective radial parameters $$a^{k_s k_l } $$ of the magnetic dipole interaction disagreed up to 300% with those known from hfs measurements of lower lying multiplets of the same configuration, even when intermediate coupling and electrostatically correlated second order hfs effects within each of the configurations are taken into account. We suggest that the main part of these discrepancies can be explained, if two-body core polarization is considered, which screens the ordinary one-body core polarization parametera 3 10 . Preliminary values for the corresponding parameters are given.

The hyperfine structure of the metastable atomic states (3d 44s 2)5 D 1,2,3,4 of53Cr has been measured using theABMR-LIRF method (atomic beam magnetic resonance detected by laser induced resonance fluorescence). The dipole coupling constantsA and the quadrupole coupling constantsB are found to beA(5 D 1)=−17.624(2) MHzB(5 D 1)=−21.847(5) MHzA(5 D 2)=−25.113(2) MHzB(5 D 2)=−13.485(5) MHzA(5 D 3)=−35.683(2) MHzB(5 D 3)=15.565(5) MHzA(5 D 4)=−48.755(2) MHzB(5 D 4)=63.021(5) MHz. From these measured hfs constants the electric quadrupole moment for53Cr is calculated to beQ=−0.15 (5) barn. The 30% error takes into account the uncertainties due to configuration interaction effects (shielding and antishielding effects) and of deviations from pure SL-coupling for the states5 D 1,2,3,4.

The hyperfine structure of the (3(d 4s)1 D 2metastable state of43Ca has been measured using theABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence). The measurements yielded for the magnetic dipole and electric quadrupole constantsA=−17.650(2) MHz andB=−4.642(12) MHz, respectively. From the measuredB factor the spectroscopic electric quadrupole moment (uncorrected for shielding effects) has been calculated to beQ(43Ca)=−0.062(12) barn. In addition, isotope shifts in the lines (3d 4s)1 D 2(3d 4p)1 F 3 0 and (3d 4s)1 D 2(4s 5p)1 p 1 0 for the stable calcium isotopes have been obtained by high resolution laser spectroscopy.

We report the hyperfine structure (hfs) measurement of the metastable (3d 6 4s 2)a 3 H 4, 5, 6 states of57Fe. The kHz-precision of these experimental results together with the hyperfine structure values of (3d 6 4s 2)a 5 D 1, 2, 3, 4, (3d 7 4s)a 5 F 2, 3, 4, 5, and (3d 7 4s)a 3 F 2, 3, 4, which were measured earlier, allowed to determine a very detailed set of effective radial parameters describing the hfs of these states, using a new parametrization method. This method treats one- and two-body contributions to the hfs separately. In this way configuration interaction effects in the hfs of the57Fe atom can be studied in detail and compared with configuration interaction effects in the fine structure of the same atom.

The results of transient loss measurements performed in a self-sustained discharge KrF* amplifier are reported. Analysis of these results gives a minimum value of 20 for the effective gain to loss ratiog 0/αeff, indicating that efficient extraction of energy in subpicosecond KrF* amplifiers in the ∼1 J range should be achievable.

The energy spectra of electrons generated by collision-free multiphoton ionization of Xe, Kr, Ar, Ne, and He irradiated at intensities up to \ensuremath{\sim}${10}^{15}$ W/${\mathrm{cm}}^{2}$ with picosecond 193-nm (6.41-eV) radiation have been studied with an energy resolution of \ensuremath{\sim}50 meV. The formation of multiply charged ions by a sequential process of ionization has been directly detected in the electron spectra by the observation of a characteristic pattern of interwoven above-threshold-ionization ladder line series. The appearance and relative intensity of specific electron lines depends strongly on the presence of near-resonances and features of the interaction involving the laser pulse shape, saturation, and the shift of the ionization threshold arising from the influence of the ponderomotive potential. The experimental results are compared qualitatively with data from ion time-of-flight experiments and with differing models of multiphoton ionization.

The hyperfine structure (hfs) of the metastable atomic states 3d64s6 D 1/2, 3/2, 5/2, 7/2, 9/2 of55Mn was measured using theABMR- LIRF method (atomicbeammagneticresonance, detected bylaserinducedresonancefluorescence). The hfs constantsA andB, corrected for second order hfs perturbations, could be derived from these measurements. The theoretical interpretation of these correctedA- andB-factors was performed in the intermediate coupling scheme taking into account the configurations 3d 54s 2, 3d 64s and 3d 7. Examining the influence of the composition of the eigenvectors on the hfs parameters $$\left\langle {r^{ - 3} } \right\rangle ^{k_s k_l } $$ it was found, that for the configuration 3d 64s the two-body magnetic interaction should be considered in the calculation of the eigenvectors. Investigating second order electrostatic configuration interactions and relativistic effects and using calculated relativistic correction factors we obtained for the nuclear quadrupole moment of the nucleus55Mn a value ofQ=0.33(1) barn, which is not perturbed by a shielding or antishielding Sternheimer factor. The following hfs constants have been obtained: $$\begin{gathered} A\left( {{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 882.056\left( {12} \right)MHz \hfill \\ A\left( {{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 469.391\left( 7 \right)MHzB\left( {{3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = - 65.091\left( {50} \right)MHz \hfill \\ A\left( {{5 \mathord{\left/ {\vphantom {5 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 436.715\left( 3 \right)MHzB\left( {{5 \mathord{\left/ {\vphantom {5 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = - 46.769\left( {30} \right)MHz \hfill \\ A\left( {{7 \mathord{\left/ {\vphantom {7 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 458.930\left( 3 \right)MHzB\left( {{7 \mathord{\left/ {\vphantom {7 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 21.701\left( {40} \right)MHz \hfill \\ A\left( {{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 510.308\left( 8 \right)MHzB\left( {{9 \mathord{\left/ {\vphantom {9 2}} \right. \kern-\nulldelimiterspace} 2}} \right) = 132.200\left( {120} \right)MHz \hfill \\ \end{gathered} $$

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Recent advances in high power laser development have enabled field strengths comparable to the atomic binding field to be generated. This experimental achievement has stimulated considerable interest in the study of the nature of multiphoton processes. Previously reported results of photoelectron spectra using 10 ps, 193 nm radiation1 have shown that the photoionization mechanism for the low charge states is largely a stepwise process and the threshold intensities required to produce the charge states are in reasonable agreement with the Keldysh model. In addition, the effect of the ponderomotive potential in suppressing the lowest order ionization channel was observed.

Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence involving studies of ion production and electron energy spectra leads to the hypothesis that the basic character of the atomic response involves highly organized coherent motions of entire atomic shells. This physical picture provides a basis for the expectation that stimulated emission in the x-ray range can be produced by direct highly nonlinear coupling of ultraviolet radiation to atoms.

The mechanism of collision-free multiphoton ionization of rare gases irradiated with ultraviolet radiation at an intensity of up to approx.10/sup 16/ W/cm/sup 2/ at 248 nm and a pulse length of approx.0.5 ps and approx.10/sup 15/ W/cm/sup 2/ at 193 nm and approx.5ps, respectively, has been studied by observing the electron energy spectra and ion charge state threshold intensities. The formation of multiply charged ions by a sequential process of ionization has been directly detected in the electron energy spectra in the form of a characterisitic pattern of interwoven above threshold ionization (ATI) ladder line series. The threshold intensities for ion production have been compared with the Keldysh model and were found to be in good agreement for light ions (Ne) and consistently lower for heavier ions (Xe), scaling with the atomic number. These measurements, together with estimates of the ion population dynamics during the rise of the laser pulse can be reasonably understood on the basis of a single electron picture. 16 refs., 5 figs.

Recently, a new experimental regime, in which the optical field strength E is considerably greater than an atomic unit ( e / a 0 2 ) , has become open for systematic study. Indeed, electric field strengths of the order of 100 ( e / a 0 2 ) should be attainable. This extraordinary range of field strengths has become accessible principally because of the availability of an ultraviolet laser technology capable of producing subpicosecond pulses with energies approaching the joule level in low divergence beams at high repetition rates. Clearly, a technology of this genre will make possible the creation of physical conditions unachievable with any other known experimental means.

It has been conjectured that atomic motions fundamentally different from those presently observed may be driven under extreme conditions of irradiation. Indeed, it has been suggested1-4 that ordered many-electron motions of outer-shell electrons could lead to enhanced rates of coupling from the radiation field to an atom. In order to study the conditions necessary for new atomic responses to occur and to determine the influence of possible damping mechanisms, the properties of ion charge state distributions,5 electron energy spectra,6 and harmonic radiation7 produced by irradiation of atoms with ultra-violet radiation with different pulse lengths, wavelengths, and intensities have been investigated.

A subpicosecond KrF laser system with peak power of the order 50 GW is described. Results of the short pulse amplification in an excimer laser amplifier have indicated that the stored energy can be efficiently extracted on a subpicosecond time scale.

In recent years a strong interest has developed in the study of the basic coupling mechanisms governing high order multiphoton processes in atomic systems. 1 Such interest has been stimulated by the rapid advances in short pulse generation techniques which allow atomic interactions at an intense field strength of the order of atomic field to be studied. Furthermore, good understanding of the highly nonlinear photon interactions is necessary to evaluate the possibility of using multiphoton processes 2 as a means to couple energy into excited states emitting in the x-ray region.

The availability of extraordinarily bright femtosecond ultraviolet sources is enabling the study of a wide range of new nonlinear phenomena. These include the possibility or ordered driven motions in atoms, molecules, and plasmas as well as processes involving collisions, even those of relativistic electrons such as electron-positron pair production. Certain aspects of these processes are discussed.

A synchronously pumped dye laser with saturable absorber jet and cavity dumper is used as the source for producing a seed beam for excimer amplifiers. An optical fiber after the dye laser and a grating pair are used to compress the dye laser pulse to 250 fsec. A two stage dye amplifier brings the pulse to about 0.1 mJ at 745.2 nm. Frequency doubling followed by summing the second harmonic with the fundamental in two KDP crystals produces radiation at 248.4 nm to be amplified in two KrF amplifiers. The UV pulse duration was measured after the first amplifier to be 450±150 fsec. The pulse energy was 23±2 mJ, and the power therefore, was nominally ∼50 GW.

Recent experimental studies1–6 of the multiple ionization of atoms generated by the collision-free interaction of intense (~ 1015 W/cm2) electromagnetic fields have shown that this class of processes exhibits several anomalous features. All of the previous work pertinent to this discussion has been conducted at a few specific wavelengths in the range between 193 nm and 10.6 µm with pulse lengths of ~ 5 ps duration or longer. Since the dynamics of the electron ejection from the atom can7 involve a time scale significantly shorter than ~ 5 ps, it is expected6 that the examination of the nonlinear coupling with intense ultraviolet radiation in the subpicosecond domain will reveal significantly modified behavior.

The availability of two intense UV-light sources operating at 193 nm (~ 5 psec, 1015 W/cm2) and 248 nm (< 0.5 psec, ~ 1016 W/cm2), respectively, has allowed comparative studies of the wavelength, pulse rise time and peak intensity dependence of the atom-field interaction.

A picosecond 248 nm KrF* laser system producing a focal intensity of greater than 1015 W/cm2 has been used to study VUV fluorescence and harmonic generation in H2, He, Ne,'Ar, Kr, and Xe. The nonlinear media were found to fall into two distinct classes: the lighter materials, H2, He, and Ne, which readily support the generation of harmonic radiation, but do not fluoresce, and the heavier materials, Ar, Kr, and Xe, which produce significant amounts of fluorescence, but in which the generation of harmonic radiation decreases rapidly with the scattering order.

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Using the method of atomic-beam magnetic resonance, detected by laser-induced resonance fluorescence (ABMR-LIRF), the atomic ground-state hyperfine intervals of 50V were precisely measured. A quadrupole moment ratio Q( 50 V ) / ( 51 V = −4.03(3) is obtained which results in Q( 50 V ) = +0.21(4) b .

The line positions and linewidths of photoelectron spectra arising from multiphoton ionization are analyzed for the first reported time in the subpicosecond (0.5–1.0-psec) region. Measurements performed with 248-nm radiation at intensity level for which the quiver energy of the free-electron motion is comparable with the photon energy are an reported. The short-pulse property causes the photoelectron energy to become a dynamical variable associated with the process of ionization and significantly influences both the line positions and the linewidths of the observed electron spectra.

A subpicosecond KrF* laser system capable of producing 20 +/- 2-mJ pulses has been developed. The means of producing ultrashort seed pulses for the KrF* amplifier system and characteristics of the full system are described. It is shown that efficient subpicosecond energy extraction is possible.

Measurements of the vacuum-ultraviolet (