Trace determination of lead by helium-4 activation analysis

The determination of lead via 30 MeV⁴He bombardment to produce the long-lived radioisotope²¹⁰Po was studied. The validity of the technique was tested by the analysis of a series of NBS glass samples doped with 61 different trace elements at nominal 500 to 1 ppm level concentrations. The measurement sensitivity of alpha counting with surface barrier detectors was evaluated. The detection limit was estimated at 0.1 ppm. The⁴He-activation technique coupled with -counting features a unique combination of sensitivity and accuracy for the trace determination of lead.     

Alpha activation of calcium and its possible use for analysis

This method is based upon the measurement of 3.95-hr⁴³Sc which is formed during α-activation from⁴⁰Ca, the most abundant (96.8%) isotope of calcium. The excitation function for the⁴⁰Ca(α, p)⁴³Sc reaction was determined and the maximum yield of⁴³Sc (about 10⁷ cpm per mg of calcium for a 1-hr irradiation at a beam current of 1 μA) was obtained at an irradiation energy of 14 MeV. The interference free sensitivity of the method at this energy was found to be 8.5·10^?12 g, for a 1-hr irradiation at a beam current of 10 μA. The elements most likely to interfere with the determination are potassium and scandium. The extent of this interference was investigated as a function of irradiation energy and methods to eliminate or subtract the activity formed from these elements are discussed. An attempt was made to determine non-destructively the calcium content of very pure silicon and aluminium and upper limits for the concentration of calcium in these samples were set at 0.27 ppb and 6.9 ppb, respectively. Magnesium, thulium oxide and yttrium oxide samples of known calcium content were also analysed.     

Simultaneous ejection of two molecular ions from keV gold atomic and polyatomic projectile impacts

We present the first experimental data on the simultaneous ejection of two molecular ions from the impact of Au(+)(n) (1< or =n< or =4) with energies ranging between 17 and 56 keV. The yields from single phenylalanine (Ph) emission, coemission of two Ph ions, and emission of the Ph dimer were measured. Large increases (1 to 2 orders of magnitude) in coemitted ion yields were observed with increasing projectile energy and complexity. Correlation coefficients were calculated for the coemission of two Ph ions; their behavior suggests differences in emission pathways for bombardment by atomic and polyatomic projectiles.     

Cycling behaviour of Li/Li4Ti5O12 cells studied by electrochemical impedance spectroscopy

We studied the behaviour of Li/Li(4)Ti(5)O(12) cells by electrochemical impedance spectroscopy to gain insight into the changes at the electrode/electrolyte interfaces during extensive cycling. A simple equivalent-circuit model is able to describe the impedance of the complete battery as a function of both state-of-charge and state-of-degradation. The formation of the solid-electrolyte interface and dendrite growth at the Li metal electrode have a strong influence on the impedance measurements although the battery performance is not significantly affected.     

On the determination of phosphorus via charged particle activation analysis

The application of charged particle activation analysis to the determination of phosphorus in a variety of sample materials is discussed. The activity produced via the³¹P(, n)^34mCl reaction is quantitated either nondestructively or using postirradiation radiochemical separations depending on the characteristics of the sample matrices. Corrections which are necessary for the determination of phosphorus in pure tantalum metal due to spectral interferences are discussed.     

Possibilities of using simultaneous ion-induced nuclear and atomic activation for the characterization of hair

The possibility of a simultaneous determination of low and medium Z elements in hair in a single ion beam exposure was studied. Different ion beams, proton, deuteron,³He and¹⁸O, at velocities ranging from 2.7–6.9 MeV/amu were investigated. In this work,¹⁸ ₈O⁴⁺ beam was found to give the best experimental condition in terms of sensitivity and number of elements detected. The detection limits in a single hair ranged from 2.9·10⁻⁵ μg for Fe to 0.72 μg for H using this beam.     

Structural characterization of organic molecules by negative ions in laser microprobe mass spectrometry. Part 2—Salts

Laser microprobe mass spectrometry (LMMS) has been applied systematically to a variety of organic polyfunctional molecules, covering a wide range of structures and polarities. The microprobe generally offers a combination of desorption under relatively mild conditions with abundant fragmentation. We attempted an empirical approach by tentative hypotheses about desorption and ionization in LMMS to consistently rationalize the detected fragments. The complementary nature of structural data, carried by positive and negative ions, is characteristic for LMMS results of non-ionic compounds. The analysis of salts represents, traditionally, an ultimate test case for soft methods in organic mass spectrometry. Hence, by a selected series of compounds, we have tried to assess to which extent the presence of preformed ions becomes an asset for LMMS analysis and affects the amount, the accessibility or the distribution of organic information between positive and negative fragments.     

Activation analysis opportunities using a 5·1012 to 5·1013 n/sec 14 MeV generator

Capabilities of 14 MeV neutron activation analysis with a high output generator are evaluated and found to be comparable with conventional activation analysis regarding sensitivity and precision; additional elements are instrumentally accessible at trace levels. Nuclear reactions featuring higher selectivity are listed and their sensitivity is compared to the present state of 14 MeV activation. Quasi-promt activation (T<1 sec) expands the scope of the technique to rapid nondestructive assays of trace species in bulk samples.     

Studies in heavy ion activation analysis

⁷Li induced radioactivation was used for the trace determination of hydrogen via the¹H(⁷Li, n)⁷ Be reaction. At 21 MeV⁷Li, only boron and magnesium present small nuclear interferences. An activation curve has been established by bombarding a stack of thin mylar foils. The comparison of this curve with the excitation function for the forward reaction, namely⁷Li(p, n)⁷ Be, shows that the recoil range from the superficial hydrogen atoms is only 1.7 mg·cm^–2, allowing post-irradiation etching. Hydrogen has been determined in titanium and lead bronze at the 100 ppm level with a relative precision of 6 to 10%. Studies of 32 potential interfering elements suggest the extension of Li activation to the trace determination of Na[²³Na(⁷Li,⁶Li)²⁴Na] and K[³⁹K(⁷Li, d)^44m,⁴⁴Sc].