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Characteristics of the 2.65 {mu}m atomic xenon laser

Description: The laser characteristics of the 2.65 {mu}m xenon laser transition are reviewed. Measured and extrapolated laser efficiency in nuclear pumped and electron beam pumped system is reported. Previous research has indicated that the reported power efficiency is between 0.1 and 2 percent.
Date: October 1, 1995
Creator: Hebner, G.A.
Partner: UNT Libraries Government Documents Department

Isoelectronic behavior of resonant and intercombination lines in MgI-like ions

Description: Radiative transitions with very different characteristic rates can serve as important diagnostics of local conditions in a plasma. Here, the observed intensity ratio of the 3s{sup 2} {sup 1}S{sub 0} - 3s3p {sup 1}P{sub 1} to the 3s{sup 2} {sup 1}S{sub 0} - 3s3p {sup 3}P{sub 1} transitions in MgI-like ions has always presented those who model plasma spectra with a challenge; the observed intensity of the intercombination line is always several times greater than what simple models predict. The authors offer a model that takes into account the contribution to the MgI-like emission features from autoionizing levels of the adjacent AlI-like charge state. Models in the present work, which include the effects of configuration interaction on ionic wavefunctions, and the contribution of both direct, impact ionization and autoionization channels from the AlI-like ion to the MgI-like ion, give good agreement with the observed resonant/intercombination (R/I) emission ratio only when a departure from ionization equilibrium is assumed. The authors also identify, for the first time, intercombination lines of the form 3s3p {sup 1}P{sub 1} - 3p{sup 2} {sup 3}P{sub 2} in several elements relevant to both astrophysical and magnetically-confined fusion plasmas.
Date: August 1, 1995
Creator: Fournier, K.B.; Goldstein, W.H.; Finkenthal, M.; Bell, R.E. & Terry, J.L.
Partner: UNT Libraries Government Documents Department

Estimates if population inversion for deep-UV transitions in Kr-like Y,Zr,Nb and Mo in a high-current reflex discharge

Description: Kr-like ions are good candidates for FUV lasing since they can be produced in plasmas quite easily. We present results from a spectroscopic investigation of Y IV emission from a high current density, cold cathode reflex discharge. The Y II to Y V emission is recorded in the 200-3000 {angstrom} range using photometrically calibrated spectrometers, while the emission of trace aluminum ions serves for plasma diagnostics. The intensities of the Y IV 4d - 5p and 5s - 5p transitions strongly increase relative to lines from Y II and Y III with increasing plasma current. The spectra studied here are obtained at a current density of 1.75 A/cm{sup 2}. Experimental Y IV intensity ratios spanning several excited configurations are compared with collisional radiative predictions of the HULLAC atomic physics package. Good agreement is found for the measured and predicted ratios of 4p{sup 5}5p to 4p{sup 5}5s level populations per statistical weight. Finally, the response of the Kr-like system to a fast, transient excitation pulse is examined using the RADEX code. Large transient gains are predicted for several 5s - 5p transitions in Y IV, Zr V, Nb VI and Mo VII.
Date: July 6, 1999
Creator: Finkenthal, M.; May, M. J.; Fournier, K.; Goldstein, W. H.; Shlyaptsev, V. N.; Soukhanovskii, V. et al.
Partner: UNT Libraries Government Documents Department

Lifetime measurements and dipole transition rates for superdeformed states in {sup 190}Hg.

Description: The Doppler-shift attenuation method was used to measure life-times of superdeformed (SD) states for both the yrast and the first excited superdeformed band of {sup 190}Hg. Intrinsic quadruple moments Q{sub 0} were extracted. For the first time, the dipole transition rates have been extracted for the inter-band transitions which connect the excited SD band to the yrast states in the second minimum. The results support the interpretation of the excited SD band as a rotational band built on an octupole vibration.
Date: March 24, 1999
Creator: Amro, H.
Partner: UNT Libraries Government Documents Department

Electron transfer and physical and chemical processes at low temperatures

Description: We summarize some phenomena that occur at temperatures of the order of 15K, and are dominated by quantum mechanical tunneling. Although electron tunneling dominates many conduction processes at low temperatures, we discuss evidence that phenomena like oxidation, as well as the solution of alkali metals in ammonia, can also be dominated by electron tunneling. Both phenomena demonstrate that the chemical potential of a metastable system can equilibrate at low temperatures by electron tunneling. The case of alkali metal clusters covered with ammonia is contrasted to covering the clusters with Xe. In this case changes in the activated conduction are observed which are consistent with the dielectric constant of the rare gas.
Date: October 1, 1995
Creator: Strongin, M.; Xia, B. & Jacobsen, F.M.
Partner: UNT Libraries Government Documents Department

Low energy gamma-transitions in Pu{sup 238} and Pu{sup 240}

Description: We investigated electron and gamma spectra of mixtures of isotopes of curium. This was done on a beta spectrometer with double focusing at an angle of {pi}{radical}2 and on a scintillation gamma spectrometer with a 40 {times} 40 mm NAI(Tl) single crystal detector. The observed electron spectrum are interpolated and presented. Also, experimental results of the ratio of conversion at L and M subshells are presented and compared to theoretical values.
Date: March 27, 1967
Creator: Akalaev, G. G.; Vartanov, N. A. & Samoilov, P. S.
Partner: UNT Libraries Government Documents Department

Overview of the current spectroscopy effort on the Livermore electron beam ion traps

Description: An overview is given of the current spectroscopic effort on the Livermore electron beam ion trap facilities. The effort focuses on four aspects: spectral line position, line intensity, temporal evolution, and line shape. Examples of line position measurements include studies of the K-shell transitions in heliumlike Kr{sup 34+} and the 2s-2p intrashell transitions in lithiumlike Th{sup 87+} and U{sup 89+}, which provide benchmark values for testing the theory of relativistic and quantum electrodynamical contributions in high-Z ions. Examples of line intensity measurements are provided by measurements of the electron-impact excitation and dielectronic recombination cross sections of heliumlike transition-metal ions Ti{sup 20+} through CO{sup 25+}. A discussion of radiative lifetime measurements of metastable levels in heliumlike ions is given to illustrate the time-resolved spectroscopy techniques in the microsecond range. The authors also present a measurement of the spectral lineshape that illustrates the very low ion temperatures that can be achieved in an EBIT.
Date: June 29, 1995
Creator: Beiersdorfer, P.; Lopez-Urrutia, J.C. & Brown, G.
Partner: UNT Libraries Government Documents Department

The role of high Rydberg states in the generation of negative ions in negative-ion discharges

Description: The generation of substantial yields of H{sup {minus}} ions in a laser excited H{sub 2} gas has been reported by Pinnaduwage and Christoforu. These H{sup {minus}} yields have been attributed to (2 + 1) REMP photoexcitation processes leading to dissociative attachment of doubly-excited or superexcited states (SES), or dissociative attachment of high Rydberg product states. The new feature of these experiments is the implied large dissociative attachment rates, of order 10{sup {minus}6} cm{sup 3} sec{sup {minus}1}, values that are orders-of-magnitude larger than the dissociative attachment of the vibrationally excited levels of the ground electronic state. While these laser excitations are not directly applicable to a hydrogen negative-ion discharge, the implication of large dissociative attachment rates to the high Rydberg states may affect both the total negative-ion density and the interpretation of discharge performance. Within the discharge energetic electrons will collisionally excite the higher Rydberg states, and the relative contribution of the dissociative attachment of these states when compared with the dissociative attachment to the ground state vibrational levels, is the topic of this paper.
Date: November 28, 1995
Creator: Hiskes, J.R.
Partner: UNT Libraries Government Documents Department

Electric field measurements from satellites-to-forbidden line ratios in an Omega-Upgrade laser-produced plasma. Semi-annual report, February 1--May 31, 1996

Description: Under this FY-96 NLUF program, the authors began their search for satellite lines to forbidden transitions for localized laser-induced electric field measurements by preparing in their laboratory a flat-field grazing incidence spectrograph for use on the OMEGA-Upgrade facility. This involved wavelength calibration using a (small) laser-produced plasma, as well as designing and constructing a mounting table compatible with the large 60-beam target chamber at LLE. Beginning in April 1996 they installed and aligned the spectrograph at LLE. Following final alignment on Monday, April 29, they obtained the following day their first time-integrated spectral data in the 30--250 {angstrom} range. A total of 28 successful shots were obtained. For most shots, two beams of the OMEGA-Upgrade laser were used at nominal uv-pulse widths of 1.1 ns and energies ranging from 76--470 J/beam, with focal spots of 80--450 {micro}m and irradiances covering approximately 10{sup 14}--10{sup 16} Watt/cm{sup 2}. Planar targets used consisted of Mg and NaF, as well as boron mounted on a plastic film, with some of the former two overcoated with 5 {micro}m of CH on each side for containing the plasma, at least during the early portion of the pulse. Preliminary analyses indicate that they do indeed observe the desired Li-like L-shell spectra for oxygen, fluorine, sodium and magnesium, as well as L-shell lines in the corresponding H-(Balmer) and He-like species. Similarly, they recorded K-shell lines from B and C. Sample traces for Mg and Na fluoride from their soft x-ray spectrograph are shown. Both of these shots were obtained at a rather low applied irradiance of 2 X 10{sup 14} W/cm{sup 2}, and were chosen mainly for line identification. The parent Li-like 2s-3p allowed lines corresponding to the forbidden-line satellites sought for E-field determinations are clearly present. The calculated satellite line intensity relative to the intensity from this ...
Date: June 15, 1996
Creator: Griem, H.R.; Elton, R.C. & Welch, B.L.
Partner: UNT Libraries Government Documents Department

Review of neon-like and nickel-like ions lasing on the J = 0 {r_arrow} 1 line using the prepulse and multiple pulse techniques

Description: The authors discuss the use of a prepulse technique to achieve lasing in low-Z neon-like ions on the 3p {r_arrow} 3s(J = 0 {r_arrow} 1) transition. Lasing has now been observed on this transitions for neon-like ions from chlorine to selenium with wavelengths ranging from 528 {angstrom} to 182 {angstrom}. For the germanium targets they present two dimensional space resolves images of the laser output with magnification of ten. Using a gas puff target as an alternative to the prepulse technique, they observe lasing at 469 {angstrom} in neon-like argon. Using a series of 100 ps pulses 400 ps apart to illuminate germanium and selenium plasmas they present results which now show the 3p {r_arrow} 3s(J = 0 {r_arrow} 1) transition to dominate the other laser lines even for selenium. Applying the multiple pulse technique to nickel-like ions they observed lasing at 79 {angstrom} on the 4d {r_arrow} 4p(J = 0 {r_arrow} 1) transition in nickel-like neodymium (Z = 60) when a series of 100--150 ps pulses which are 400--500 ps apart are used to illuminate slab targets of neodymium. To maximize the laser output for neodymium they combine the advantages of coupling two slab targets, using the traveling wave geometry, and curving the target surface.
Date: November 1, 1995
Creator: Nilsen, J.; Moreno, J.C.; Da Silva, L.B.; Barbee, T.W. Jr.; Li, Y.; Lu, P. et al.
Partner: UNT Libraries Government Documents Department

Piezoelectric Effects on the Optical Properties of GaN/Al(x)Ga(1-x)N Multiple Quantum Wells

Description: Piezoelectric effects on the optical properties of GaN/AlGaN multiple quantum wells (MQWS) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. For MQWS with well thickness 30 and 40 the excitonic transition peak positions at 10 K in continuous wave (CW) spectra are red-shifted with respect to the GaN epilayer by 17 meV and 57 meV, respectively. The time-resolved PL spectra of the 30 and 40 well MQWS reveal that the excitonic transition is in fact blue-shifted at early delay times due to quantum confinement of carriers. The spectral peak position shifts toward lower energies as the delay time increases and becomes red-shifted at longer delay times. We have demonstrated that the results described above is due to the presence of the piezoelectric field in the GaN wells of GaN/AlGaN MQWS subject to elastic strain together with screening of the photoexcited carriers. By comparing experimental and calculation results, we conclude that the piezoelectric field strength in GaN/Al.15G~.85N MQWS has a lower limit value of about 560 kV/cm: The electron and hole wave function distributions have also been obtained. The implication of our findings on the practical applications of GaN based optoelectronic devices is also discussed.
Date: November 10, 1998
Creator: Botchkarev, A.; Chow, W.W.; Jiang, H.X.; Kim, H.S.; Lin, J.Y. & Morkoc, H.
Partner: UNT Libraries Government Documents Department

Test of {Delta}I = 2 staggering in the superdeformed bands of {sup 194}Hg

Description: The presence of {Delta}I = 2 staggering in the three known superdeformed bands of {sup 194}Hg has been reexamined in a new experiment with Gammasphere. A relative accuracy of better than 30 eV was achieved for most transition energies. No statistically significant oscillations in the transition energies were found for band 1 while staggering patterns were observed in bands 2 and 3. The statistical significance of the observed effects was analyzed. The patterns display some similarities with expectations based on a band crossing picture, even though such a picture cannot reproduce the observations in a straightforward way. No evidence was found for additional superdeformed bands in {sup 194}Hg which could account for possible band-crossings.
Date: June 5, 1996
Creator: Kruecken, R.; Deleplanque, M.A.; Lee, I.Y. & Asztalos, S.
Partner: UNT Libraries Government Documents Department

Photophysics of fullerenes: Thermionic emission

Description: Multiphoton ionization of fullerenes using long-pulse length lasers occurs mainly through vibrational autoionization. In many cases the laser ionization can be described as thermionic in analogy to the boiling off of electrons from a filament. Thermionic emission manifests itself as a delayed emission of electrons following pulsed laser excitation. Klots has employed quasiequilibrium theory to calculate rate constants for thermionic emission from fullerenes which seem to quantitatively account for the observed delayed emission times and the measured electron energy distributions. The theory of Klots also accounts for the thermionic emission of C{sub 60} excited by a low power CW Argon Ion laser. Recently Klots and Compton have reviewed the evidence for thermionic emission from small aggregates where mention was also made of experiments designed to determine the effects of externally applied electric fields on thermionic emission rates. The authors have measured the fullerene ion intensity as a function of the applied electric field and normalized this signal to that produced by single photon ionization of an atom in order to correct for all collection efficiency artifacts. The increase in fullerene ion signal relative to that of Cs{sup +} is attributed to field enhanced thermionic emission. From the slope of the Schottky plot they obtain a temperature of approximately 1,000 K. This temperature is comparable to but smaller than that estimated from measurements of the electron kinetic energies. This result for field enhanced thermionic emission is discussed further by Klots and Compton. Thermionic emission from neutral clusters has long been known for autodetachment from highly excited negative ions. Similarly, electron attachment to C{sub 60} in the energy range from 8 to 12 eV results in C{sub 60} anions with lifetimes in the range of microseconds. Quasiequilibrium theory (QET) calculations are in reasonable accord with these measurements.
Date: September 1, 1996
Creator: Compton, R.N.; Tuinman, A.A. & Huang, J.
Partner: UNT Libraries Government Documents Department

Enhanced negative ion formation via electron attachment to electronically-excited states

Description: Recent basic studies on electron attachment to laser-excited molecules show that electron attachment to electronically-excited states can have orders of magnitude larger cross sections compared to the respective ground electronic states. Even though systematic studies have not been conducted, there are indications that electronically-excited states may play a significant role in negative ion formation in gas discharges. The high-lying Rydberg states could be of particular significance since, (i) their production efficiencies are high, and (ii) they have comparatively long lifetimes. Such states could be populated in discharge sources via direct electron impact or via excitation transfer from metastable states of inert gases.
Date: December 31, 1995
Creator: Pinnaduwage, L.A.
Partner: UNT Libraries Government Documents Department

Spectroscopy at the high-energy electron beam ion trap (Super EBIT)

Description: The following progress report presents some of the x-ray measurements performed during the last year on the Livermore SuperEBIT facility. The measurements include: direct observation of the spontaneous emission of the hyperfine transition in ground state hydrogenlike holmium, {sup 165}Ho{sup 66{plus}}; measurements of the n {equals} 2 {r_arrow} 2 transition energies in neonlike thorium, Th{sup 80{plus}}, through lithiumlike thorium, Th{sup 87{plus}}, testing the predictions of quantum electrodynamical contributions in high-Z ions up to the 0.4{percent} level; measurements of the isotope shift of the n= 2 {r_arrow} 2 transition energies between lithiumlike through carbonize uranium, {sup 233}U{sup 89{plus}...86{plus}} and {sup 238}U{sup 89{plus}...86{plus}}, inferring the variation of the mean- square nuclear charge radius; and high-resolution measurements of the K{alpha} radiation of heliumlike xenon, Xe{sup 52 {plus}}, using a transmission-type crystal spectrometer, resolving for the first time the ls2p{sup 3}P{sub 1} {r_arrow} 1S{sup 2} {sup 1}S{sub 0} and ls2s{sup 3}S{sub 1} {r_arrow} 1S{sup 2} {sup 1}S{sub 0} transitions individually. 41 refs., 9 figs., 1 tab.
Date: July 10, 1996
Creator: Widmann, K.; Beiersdorfer, P. & Crespo Lopez-Urrutia, J.R.
Partner: UNT Libraries Government Documents Department

An experiment to demonstrate a nitrogen recombination X-ray amplifier using high-density planar gas jet laser target. Final report

Description: The results of an experiment to search for lasing in atomic transitions at x-ray energies in N{sub 2} gas target plasmas using ultra-short laser pulses is presented. Particular emphasis was placed on a search for a predicted 24.7 nm optical-field-ionization (OFI) induced lasing line from the Li-like nitrogen (N{sup 4+}, 3d {yields} 2p) transition. The excitation laser was a multi-terawatt Cr:LiSrAlF{sub 6} laser system operating at a wavelength of 825 nm and a pulse duration of 135 fs located at the Lawrence Livermore National Laboratory. Experimental conditions were optimized and a series of Li-like (including the 24.7 rm N{sup 4+} 3d {yields} 2p) lines were observed and identified. Further experimental studies are required before an attempt at measurement of any potential lasing gain can be made.
Date: March 31, 1996
Creator: Pronko, J.G. & Kohler, D.
Partner: UNT Libraries Government Documents Department

Photodissociation spectroscopy and dynamics of the vinoxy (CH{sub 2}CHO) radical

Description: The photodissociation spectroscopy and dynamics of the vinoxy (CH{sub 2}CHO) radical have been studied using fast beam photofragment translational spectroscopy. The photodissociation cross section over the B{sup 2}A{double_prime} {l_arrow} X{sup 2}A{double_prime} band is measured, and photofragment translational energy and angular distributions are obtained at several excitation energies. For CH{sub 2}CHO, predissociation is observed over the entire band, including several transitions near the band origin which were seen previously in laser-induced fluorescence experiments. Two dissociation channels are seen: CH{sub 3} + CO and H + CH{sub 2}CO. The CH{sub 3} + CO channel was investigated in considerable detail and appears to proceed via internal conversion to the CH{sub 2}CHO ground state followed by isomerization to CH{sub 3}CO and subsequent dissociation. The translational energy distributions for this channel suggest an isomerization barrier in the range of 2 eV with respect to CH{sub 3} + CO products.
Date: November 1, 1995
Creator: Osborn, D.L.; Choi, H. & Neumark, D.M.
Partner: UNT Libraries Government Documents Department

Critical tests of line broadening theories by precision measurements

Description: The spectral line profiles of ionized emitters in plasmas play an important role in the calculation of opacity, for short-wavelength laser studies, and for the diagnostics of inertial confinement fusion plasmas. Sophisticated theoretical methods and modeling have been advanced and applied in recent years to calculate spectral line profiles in the limits where broadening by electron collisions or by ion microfield dominates. Here, the authors describe recent measurements of spectral line profiles of a z-pinch experiment employing precision plasma diagnostic techniques. In particular, the electron-collisional-broadened 2s--2p transitions in B{sub III} have been investigated because their line profiles provide an excellent test for electron-impact line shape theories and electron collision strength calculations. Although they find good agreement with semiclassical calculations, a factor of two discrepancy with the most elaborate quantum-mechanical five-state close coupling calculations is observed. They discuss the experimental error estimates of the various measured quantities and show that the observed discrepancy can not be explained by experimental shortcomings. They further discuss measurements of non-isolated spectral lines of some {Delta}n = 1 transitions in C{sub IV}--O{sub VI}. For these transitions ion broadening dominates. Excellent agreement for the whole line profile with line broadening calculations is obtained for all cases only when including ion dynamic effects. The latter are calculated using the frequency-fluctuation model and account for about 10--25% of the line width of the considered ions.
Date: February 22, 1996
Creator: Glenzer, S.H.
Partner: UNT Libraries Government Documents Department

2l-nl{prime} x-ray transitions from neonlike charge states of the row 5 metals with 39 {le} Z {le} 46

Description: X-ray spectra of 2l-2l{prime} transitions with 3 {le} n {le} 12 in the row five transition metals zirconium (Z = 40), niobium (Z = 41), molybdenum (Z = 42) and palladium (Z = 46) from charge states around neonlike have been observed from Alcator C-Mod plasmas. Accurate wavelengths ({+-} .2 m{angstrom}) have been determined by comparison with neighboring argon, chlorine and sulfur lines with well known wavelengths. Line identifications have been made by comparison to ab initio atomic structure calculations, using a fully relativistic, parametric potential code. For neonlike ions, calculated wavelengths and oscillator strengths are tabulated for 2p-nd transitions in Y (Z = 39), Tc (Z = 43), Ru (Z = 44) and Rh (Z = 45) with n = 6 and 7. The magnitude of the configuration interaction between the (2p{sup 5}){sub 1/2}6d{sub 3/2} J = 1 level and the (2p{sup 5}){sub 3/2}7D{sub 5/2} J = 1 levels is demonstrated as a function of atomic number for successive neonlike ions. Measured spectra of selected transitions in the aluminum-, magnesium-, sodium- and fluorine like isosequences are also shown.
Date: March 18, 1996
Creator: Rice, J. E.; Terry, J. L.; Marmar, E. S.; Fournier, K. B.; Goldstein, W. H.; Finkenthal, M. et al.
Partner: UNT Libraries Government Documents Department

High resolution two-dimensional near field images of neon-like soft x- ray lasers

Description: We discuss high resolution two-dimensional near-field images of the neon-like nickel and germanium X-ray laser. The Asterix iodine laser, using a prepulse 5.23 ns before the main pulse, was used to irradiate slab targets. Our imaging diagnostic consisted of a concave multilayer mirror that imaged the X-ray laser line (with a magnification of ten) onto a backside illuminated X-ray CCD detector. A great deal of structure was observed in the near field images, particularly in the J=0-1 emission. We observed a large difference in the spatial dependence of the J=0-1 and J=2-1 lines of germanium, with the J=2-1 emission peaking farther away from the original target surface. The prepulse level was varied and observed to have a significant effect on the spatial dependence of the germanium and nickel laser lines. A larger prepulse moved the peak emission farther away from the target surface. These measurements are generally consistent with hydrodynamic simulations coupled with atomic kinetics.
Date: June 1, 1996
Creator: Moreno, J. C.; Nilsen, J.; Li, Y; Lu, P. & Fill, E.E.
Partner: UNT Libraries Government Documents Department

Laboratory astrophysics: Measurements of n = n{prime} to n = 2 line emission in Fe{sup 16+} to Fe{sup 23+}

Description: One of the dominant forms of astronomical line emission in the 6 {angstrom} to 18 {angstrom} spectral region is line emission produced by n = n{prime} to n = 2 transitions in Fe{sup 16+} to Fe{sup 23+} (i.e., Fe L-shell n-2 line emission). Using the Lawrence Livermore National Laboratory electron beam ion trap (EBIT) facility, the authors have carried out a number of measurements designed to address astrophysical issues concerning Fe L-shell line emission. Desired ions are produced and trapped using the nearly monoenergetic electron beam of EBIT. Trapped ions are collisionally excited and the resulting X-ray line emission detected using Bragg crystal spectrometers. They have recently completed a line survey of Fe L-shell 3-2 line emission. The line survey will allow a more reliable accounting of line blending in astronomical spectra. They have now begun a series of broadband, high resolution line ratio measurements. These measurements are designed to benchmark atomic calculations used in astronomical plasma emission codes and also for comparison with X-ray spectral observations of astronomical objects. Initial measurements have been carried out in Fe{sup 23+}. Preliminary results agree with distorted wave calculations to within 20% and better.
Date: March 5, 1996
Creator: Savin, D.W.; Beiersdorfer, P.; Lopez-Urrutia, J.C.; Decaux, V.; Liedahl, D.A.; Reed, K.J. et al.
Partner: UNT Libraries Government Documents Department

EBIT (Electron Beam Ion Trap), N-Division Experimental Physics. Annual report, 1994

Description: The experimental groups in the Electron Beam Ion Trap (EBIT) program continue to perform front-line research with trapped and extracted highly charged ions (HCI) in the areas of ion/surface interactions, atomic spectroscopy, electron-ion interaction and structure measurements, highly charged ion confinement, and EBIT development studies. The ion surface/interaction studies which were initiated five years ago have reached a stage where they an carry out routine investigations, as well as produce breakthrough results towards the development of novel nanotechnology. At EBIT and SuperEBIT studies of the x-ray emission from trapped ions continue to produce significant atomic structure data with high precision for few electron systems of high-Z ions. Furthermore, diagnostics development for magnetic and laser fusion, supporting research for the x-ray laser and weapons programs, and laboratory astrophysics experiments in support of NASA`s astrophysics program are a continuing effort. The two-electron contributions to the binding energy of helium like ions were measured for the first time. The results are significant because their precision is an order of magnitude better than those of competing measurements at accelerators, and the novel technique isolates the energy corrections that are the most interesting. The RETRAP project which was initiated three years ago has reached a stage where trapping, confining and electronic cooling of HCI ions up to Th{sup 80+} can be performed routinely. Measurements of the rates and cross sections for electron transfer from H{sub 2} performed to determine the lifetime of HCI up to Xe{sup q+} and Th{sup q+} (35 {le} q {le} 80) have been studied at mean energies estimated to be {approximately} 5 q eV. This combination of heavy ions with very high charges and very low energies is rare in nature, but may be encountered in planned fusion energy demonstration devices, in highly charged ion sources, or in certain astrophysical events.
Date: October 1, 1995
Creator: Schneider, D.
Partner: UNT Libraries Government Documents Department

Atomic emission spectroscopy in high electric fields

Description: Pulsed-power driven ion diodes generating quasi-static, {approximately}10 MV/cm, 1-cm scale-length electric fields are used to accelerate lithium ion beams for inertial confinement fusion applications. Atomic emission spectroscopy measurements contribute to understanding the acceleration gap physics, in particular by combining time- and space-resolved measurements of the electric field with the Poisson equation to determine the charged particle distributions. This unique high-field configuration also offers the possibility to advance basic atomic physics, for example by testing calculations of the Stark-shifted emission pattern, by measuring field ionization rates for tightly-bound low-principal-quantum-number levels, and by measuring transition-probability quenching.
Date: December 31, 1995
Creator: Bailey, J.E.; Filuk, A.B. & Carlson, A.L.
Partner: UNT Libraries Government Documents Department

Competing structures in nuclei near closed shells. Final report, September 1, 1993--November 30, 1996

Description: This report summarizes the progress made during this period. A series of experiments on levels in {sup 144}Nd have led to the identification of quadrupole-octupole coupled states in the nucleus. These experiments included the measurement of excited level lifetimes using the GRID technique, the measurement of transition conversion coefficients and the measurement of weak transition intensities. A fast electronic timing system has been set-up at Tennessee Tech. This system can be used to measure nuclear excited state lifetimes in the range from 5 ps upward. A new variation of the centroid shift method has been developed which eliminates the need to determine a prompt position. This centroid difference method employs both forward and reverse gating of gamma cascades to generate two timing spectra.
Date: February 1, 1999
Creator: Robinson, S.J.
Partner: UNT Libraries Government Documents Department