Precision measurement with visual feedback using binary phase diffractive optical elements

A novel method for obtaining precision measurements by using two binary diffractive optical elements is presented. The system provides visual feedback of the measurement without the use of electronics.     

Fit values of N subshell fluorescence yields and Coster-Kronig yields for elements with 38?Z?103

Most probable values of Coster-Kronig (CK) transition probabilities (S₁₂, S₁₃, S₁₄, S₁₅, S_1,67, S₂₃, S₂₄, S_2,67, S₃₄, S₃₅, S₃₅, S_3,67, S₄₅ and S_4,67) and N_i subshell fluorescence yields (N₁, N₂, N₃, N₄, N₅ and N₆₇) have been determined by using least-squares fitted to obtain the polynomials, which is plotted by using the McGuire's values (Phys Rev A 9(5) (1974) 1840), representing them as a function of atomic number. The S_ij represents the N subshell vacancy transitions from ith subshell to jth subshell. The obtained values of N_i subshell fluorescence yields—N₁, N₂, N₃, N₄, N₅, N₆₇, and CK transition probabilities—S₁₂, S₁₃, S₁₄, S₁₅, S_1,67, S₂₃, S₂₄, S_2,67, S₃₄, S₃₅, S₃₅, S_3,67, S₄₅ and S₄₆ are presented.     

5f localization in actinide elements at high temperatures

It is suggested that the itenerant 5f electrons in plutonium and neptunium become localized at high temperatures close to melting. This conclusion is supported by unusually large thermal expansions and recent observation of high temperature β-Np structure in trivalent scandium under pressure.     

Projectile fluorescence yields in heavy ion collisions

Fluorescence yields of highly ionized projectiles entering thin solid foils are determined from a target-thickness analysis of projectile and target K X-ray cross sections. Values are obtained for 20–80 MeV Cl ions on Cu and compared with scaling calculations.     

Fission fragment angular distribution in alpha-particle-induced fission of actinide elements

Using Lexan polycarbonate plastic as the fission fragment track detectors, the fragment angular distributions have been measured in the cases of fission of²³²Th and²³⁸U induced by alpha particles of various energies ranging from 40 to 70MeV obtained from the 88″ variable energy cyclotron at Calcutta. The center-of-mass angular distributions have been calculated and fitted by a series of Legendre polynomials. TheW(10°)/W(90°) ratios (defined as anisotropy) were measured at several energies for both the targets. These data are utilized in calculation of the energy dependence ofK ₀ ² , the standard deviation of the distribution in the angular momentum projection on the nuclear symmetry axis at the saddle point. Values of Γ _f /Γ _η , i.e. the ratio of the fission width to neutron emission width have been determined for²³²Th and²³⁸U nuclei. The integral cross-section for alpha induced fission in each target was determined by numerical integration of the respective center-of-mass angular differential cross-sections. The results were compared with similar data available in the literature which served to resolve some of the discrepancies observed in earlier measurements. The results were also compared with theoretical cross-sections.     

Precision determination of high-Z K-shell fluorescence yields from195Au,207Bi,and235Np decays

A new method utilizing a cooled, high resolution, windowless Si(Li) x-ray and Auger electron detector has been developed for the accurate measurement of high-Z K-shell fluorescence yields. With this method, values of theK-fluorescence yield ω _k have been determined with high accuracy atZ=78, 82, and 92 from the radioactive decay of carrier-free¹⁹⁵Au,²⁰⁷Bi, and²³⁵Np, respectively. The values of ω _k are 0.968±0.008, 0.972±0.008, and 0.970±0.005, respectively where the error limits represent 95% confidence. In addition, relativeK-Auger electron group intensities atZ=92 were measured and found to be(K-LL)∶(K-LX)∶(K-XY)=100∶(65.2±6.0)∶ (8.1±0.8). The experimental results for ω _k are compared with the relativistic calculations of Bhalla, Ramsdale and, Rosner, and satisfactory agreement is found.     

Structural and electronic relationships between the lanthanide and actinide elements

The similarity and difference between the solid state properties of the 4f and 5f transition metals are pointed out. The heavier 5f elements show properties which have direct correspondence to the early 4f transition metals, suggesting a localized behaviour of the 5f electrons for those metals. On the other hand, the fact that Pu metal has a 30% lower volume than its neighbour heavier element, Am, suggests a tremendous difference in the properties of the 5f electrons for this element relative to the heavier actinides. This change in behaviour between Pu and Am can be viewed as a Mott transition within the 5f shell as a function of the atomic number Z. On the metallic 5f side of the Mott transition (i.e., early actinides), the elements show most unusual crystal structures, the common feature being their low symmetry. An analogous behaviour for the lanthanides is found in cerium metal under compression, where structures typical for the light actinides have been observed experimentally. A generalized phase diagram for the actinides is shown to contain features comparable to the individual phase diagram of Ce metal. The crystal structure behaviour of the lanthanides and heavier actinides is determined by the number of 5d (or 6d) electrons in the metallic state, since for these elements the f electrons are localized and nonbonding. For the earlier actinide metals electronic structure calculations - where the 5f orbitals are treated as part of the valence bands - account very well for the observed ground state crystal structures. The distorted structures can be understood as Peierls distortions away from the symmetric bcc structure and originate from strongly bonding 5f electrons occupying relatively narrow 5f states. High pressure is an extremely useful experimental tool to demonstrate the interrelationship between the lanthanides and the actinides. This revised version was published online in July 2006 with corrections to the Cover Date.     

Precision measurements of x-ray energies,natural widths and intensities in the actinide region

A Dumond-type curved crystal spectrometer has been used to measureK x-ray energies, natural widths and relative intensities for the eleven actinides from₈₈Ra to₉₈Cf. The results are compared to the most recent theoretical predictions.     

K-shell fluorescence yields for potassium and calcium compounds

The K-shell fluorescence yields for potassium and calcium compounds were investigated using a Si(Li) X-ray detector system ( at ). The target samples were excited using gamma rays from an ²⁴¹Am annular source of strength . Chemical effects on K-shell fluorescence yield for potassium and calcium were observed. The values were compared with theoretical values of pure potassium and calcium.     

Precision measurement with atom interferometry

Development of atom interferometry and its application in precision measurement are reviewed in this paper. The principle, features and the implementation of atom interferometers are introduced, the recent progress of precision measurement with atom interferometry, including determination of gravitational constant and fine structure constant, measurement of gravity, gravity gradient and rotation, test of weak equivalence principle, proposal of gravitational wave detection, and measurement of quadratic Zeeman shift are reviewed in detail. Determination of gravitational redshift, new definition of kilogram, and measurement of weak force with atom interferometry are also briefly introduced.     

Precision two-photon spectroscopy of alkali elements

In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6s ² S _1/2 level of ³⁹K and ⁴¹K, 9s ² S _1/2level and 7d ² D _3/2 level of ¹³³Cs are also discussed.     

Precision measurement of cosmic-Ray antiproton spectrum

The energy spectrum of cosmic-ray antiprotons ( &pmacr;'s) has been measured in the range 0.18-3.56 GeV, based on 458 &pmacr;'s collected by BESS in a recent solar-minimum period. We have detected for the first time a characteristic peak at 2 GeV of &pmacr;'s originating from cosmic-ray interactions with the interstellar gas. The peak spectrum is reproduced by theoretical calculations, implying that the propagation models are basically correct and that different cosmic-ray species undergo a universal propagation. Future BESS data with still higher statistics will allow us to study the solar modulation and the propagation in detail and to search for primary &pmacr; components.     

Precision position measurement of single atom

Atom localization in a five-level atomic system under the effect of three driving fields and one standing wave field is suggested. A spontaneously emitted photon from the proposed system is measured in a detector. Precision position measurement of an atom is controlled via phase and vacuum field detuning without considering the parity violation.     

Two mode fission: Existence of two independent paths in the fission of actinide elements

We attempted to confirm the existence of two-mode-fission mechanism in the²³²Th and²³⁸U plus⁴He systems. Angular distributions and differential ranges of the fission fragments were measured for both systems. Two distinct groups, symmetric and asymmetric, were observed in the anisotropy of the fragments obtained from the angular distributions in either systems. Kinetic energies of the fragments were deduced from the measured ranges and the effective distances were calculated from the data. The distribution of the resulting distances was classified into two groups also, indicating the existence of the symmetric and asymmetric modes. This strongly suggests existence of two independent paths in the fission process.Communicated by: P. Armbruster     

TheL 1 subshell fluorescence and Coster-Kronig yields forZ=96

High resolution Si(Li)-Si(Li) and Si(Li)-Ge(Li) detector arrangements have been used to studyL x-ray spectra in coincidence withL-shell internal conversion electrons, gamma rays, andK x-rays emitted in²⁴⁹Cf decay. TheL ₁ subshell fluorescence and Coster-Kronig yields determined forZ=96 from these spectra are ω₁=0.25±0.06,f ₁₂≦0.10, andf ₁₃=0.69 ±0.08. The presence of theL ₁-L ₃ radiative transition is also further confirmed in this work.     

Dependence of K-shell fluorescence yields on multiplet states of neon

The K-shell fluorescence yields are calculated to be equal to 0.013 and 0.028 respectively for ³P and ¹P multiplet states of 1s¹ 2s² 2p⁵ configuration of neon. This observation can significantly effect analyses of ion-atom collision experiments where in X-ray production cross-sections are measured.     

A new technique for the measurement of sputtering yields

We have measured the yields of 90 keV ⁴⁰Ar⁺ and V⁴He⁺ sputtering of Mo and V samples by the use of a new radio-tracer technique. This technique involves activating the samples by high-energy charged-particle irradiation before sputtering, and using conventional γ-ray counting methods to analyze the material subsequently sputtered onto collector foils. We have also measured angular distributions of the sputtered material, and compared these results and our total sputtering yields with the predictions of Sigmund's sputtering theory. Further comparisons between our radiotracer results and those obtained for ⁴⁰Ar⁺ sputtering of unactivated Mo and V samples, determined from elastic backscattering measurements using 12 MeV ¹⁶O ions, show that the techniques give consistent results.