A novel method to determine degradation constants has been developed for energetic ^7*Li ions produced from the ¹⁰B (n, α) ^7*Li reaction, moving in liquid media. The energetic ^7*Li generated in a thin boron film on silicon wafer plunged into a liquid sample in which the wafer was immersed. The degradation constants were determined by analyzing the Doppler-broadened lineshapes of prompt γ-ray at 478 keV emitted from ^7*Li. For comparison, degradation constants were also measured for solutions of boron compounds. Values obtained by the two methods gave fair agreement.

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The adsorption properties of newly developed ¹⁸⁸Re complexes with aminomethylenephosphonate (amp) (EDTMP-Ethylenediamine-N, N, N', N'-tetrakis(methylenephosphonic acid), EDBMP-Ethylenediamine-N, N'-bis(methylenephosphonic acid) and NTMP-Nitrilotris(methylenephosphonic acid)) on hydroxyapatite was investigated. The adsorption of ¹⁸⁸Re complexes was strongly affected by pH and ionic strength in a solution. The adsorption coefficient(ml/g), which is defined by the ratio of the concentration of the complex per unit weight of the hydroxy-apatite to the concentration in unit volume of the solution, increased with decreasing pH and ionic strength. These observations suggest that one of the causes of the adsorption of ¹⁸⁸Re-amp is considered to be the electrostatic forces between the negative ¹⁸⁸Re-amp complex and the positive HAP surface. The adsorption affinity of the ¹⁸⁸Re-amp complex for HAP increased in the order of ¹⁸⁸Re-EDBMP<¹⁸⁸Re-NTMP<¹⁸⁸Re-EDTMP. Furthermore, the adsorption coefficient of carrier-free ¹⁸⁸Re-EDTMP was larger than that of carrier-added one under the same conditions. From a detailed comparison of the effect of the Re carrier concentration on the adsorption coefficient of ¹⁸⁸Re-EDTMP with its structural analysis by HPLC, we concluded that the Re carrier effect on the adsorption coefficient was caused by the different distribution of the components in the ¹⁸⁸Re-EDTMP mixture between the carrier-free and the carrier-added complex.

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The characteristics of the phase transfer of UO₂²⁺ across aqueous(w)/nitrobenzene(nb) solutions interface in the presence of octyl(phenyl)-N, N-diisobutylcarbamoyl-methylphosphine oxide (CMPO) as an ionophore were investigated by cyclic voltammetry (VITIES) and polarography (PITIES) for ion transfer at the interface of two immiscible electrolyte solutions. The transfer of UO₂²⁺ from w to nb is remarkably facilitated by CMPO and the ion transfer reaction exhibits an irreversible nature. The rate-determining step of the UO₂²⁺ transfer is assigned to adsorption / desorption process of the UO₂²⁺-CMPO complex at the w/nb interface. The ion transfer potential of UO₂²⁺ shifts more positively when the two phase system is allowed to stand stationarily for a given time before the measurement of the cyclic voltammogram. The potential shift with the standing time is attributable to a decrease in the interfacial concentration of “free” CMPO due to the protonation of CMPO followed by the accumulation of the ion pair between HCMPO⁺ and TPhB^- at the w/nb interface.

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A characteristic that sets radioactivity measurements apart from most spectrometries is that the precision of a single determination can be estimated from Poisson statistics. This easily calculated counting uncertainty permits the detection of other sources of uncertainty by comparing observed with a priori precision. A good way to test the many underlying assumptions in radiochemical measurements is to strive for high accuracy. For example, a measurement by instrumental neutron activation analysis (INAA) of gold film thickness in our laboratory revealed the need for pulse pileup correction even at modest dead times. Recently, the International Organization for Standardization (ISO) and other international bodies have formalized the quantitative determination and statement of uncertainty so that the weaknesses of each measurement are exposed for improvement. In the INAA certification measurement of ion-implanted arsenic in silicon (Standard Reference Material 2134), we recently achieved an expanded (95% confidence) relative uncertainty of 0.38% for 90 ng of arsenic per sample. A complete quantitative error analysis was performed. This measurement meets the CCQM definition of a primary ratio method.

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The ²³⁴U/²³⁸U activity ratios of 45 products from 6 volcanoes of Izu-Mariana island-arc ranged from 0.96 to 1.04, representing a Gaussian distribution with the average value of 0.997 and the standard deviation of 0.014. The result indicates that ²³⁴U is in radioactive equilibrium with ²³⁸U in the erupting magmas from island-arc volcanoes.

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Temperature-dependent ⁵⁷Fe Mössbauer effect studies have been carried out on organge needle-shaped crystals of acetyl ferrocene over the range 90≤T≤350 K in an effort to elucidate the motional behavior of the metal atom up to temperatures near the melting point (359K). The spectra consist of one well resolved doublet at all temperatures, with an isomer shift of 0.554±0.002 and 0.438±0.001 mm s^-1 at 90 and 298K, respectively. The temperature dependence of the isomer shift corresponds to an effective vibrating mass of 74±2 daltons, and, in conjunction with the temperature dependence of the recoil-free fraction, to a Mössbauer lattice temperature of 134K. There is a small but significant vibrational anisotropy of the metal atom motion evident in the spectroscopic data above ∼ 200K.

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Accelerator mass spectrometry (AMS) is an ultrasensitive measure for tracing ¹⁴C labeled molecules in vivo or detecting the biomarker for assessment of carcinogenesis. Basic principles, wide applications and new progresses of bio-¹⁴C-AMS have been presented. It is a state-of-the-art tool for measuring the adduction of biological molecules with xenobiotics, including carcinogens, drugs, agrochemicals, nicotine etc. . We have studied the genotoxicity and proteins adduction of smoking specific nicotine and its nitrosamine derivative NNK since 1994. The successful applications have proven the effectiveness of AMS in assessment of cancer risk, screening of drug toxicity and studies of nutrient uptake. In particular, AMS is characterized by measuring xenobiotics at very low dose levels relevant to human environmental exposure. It is sensitive and precise to an attomole (10^-18 mole) of ¹⁴C per mg carbon. Although it has some shortcomings, undoubtedly, AMS possesses an evident merit of high sensitivity and will have widespread applications in the biomedical sciences.

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Following an overview on the nature of bonding of such hypervalent molecules as Li_nA (Li₆C, Li₃O, Li₄O, Li₃S, Li₄S, Li₄P) and M₂CN (M=Li, Na, K), the present paper deals with the molecular and electronic structures of newly found lithium-rich Li₂F and Li₂OH molecules as well as Li₂F_n-1 (n=3, 4) and Li_n (OH) _n-1 (n=3-5) clusters which have been detected in supersonic beams effusing from a laser ablation source. The ionization energies (IEs) determined by photoionization were 3.78±0.2 eV for Li₂F, 4.32±0.2 eV for Li₃F₂, and 4.30±0.2 eV for Li₄F₃. Agreements of thhse IEs with theoretical ones calculated by ab initio MO methods support that Li₂F is in a hyperlithiated configuration (HLC) in which the excess electron delocalizes over the two lithiums, while Li₃F₂ and Li₄F₃ are in a segregated configuration (SC) comprising ionic and non-ionic lithiums resulting from localization of the excess valence electron. Ionization efficiency curves (IECs) measured for Li_n (OH) _n-1 (n=2-5) are well reproduced with a simulation involving Franck-Condon factors, and this enabled us to identify the global-minimum structure of these species predicted by theoretical calculations with the DFT method. The IEs determined were 4.053±0.003 eV for Li₂OH in HLC, 3.687±0.003 eV for Li₃ (OH) ₂ in HLC, 4.133±0.003 eV for Li₃ (OH) ₂ in SC, and 3.418±0.009 eV for Li₄ (OH) ₃ in SC, and 3.60±0.11 eV for Li₅ (OH) ₄ in SC. Also, IE of Li₃O was determined as 3.59±0.02 eV from reinvestigation with the photoionization technique. Furthermore, Li₃O was found to be a floppy molecule sharing both the D_3h and C_2v structures from a precise analysis of the observed IEC taking account of the potential energy surface for both neutral and cationic Li₃O. This is the first experimental evidence for “electronomers” or electronic isomers of Li₃O, which have nearly the same stability but are different in localization of the SOMO. It is eventually stressed that delocalization of the excess valence electron over all of the lithium atoms in a molecule is essential to afford hyperlithiated molecules and that the shape of SOMO or HOMO, which accommodates the excess valence electron or electrons, plays a key role in determining the stability of hyperlithiated molecules.

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Free volume effects are important for positronium formation, pick-off annihilation and chemical reactions. In order to turn positron annihilation lifetime (PAL) measurements into effective tool for quantitative investigations of molecular solids, polymers for example, the relation between the intensity of the long-lived positronium component of lifetime distribution of positron annihilation and concentration of defects (elementary free volumes EFV) has to be derived. This enables not only calculations of the effective size of elementary free volumes but also estimations of the specific free volume. Meanwhile, the studies of EFV in polymer systems are of great interest, because effective sizes and concentrations of EFV determine many transport, mechanical and other properties of polymers. We demonstrate here an approach to the studies of these problems on example of big group of glassy polymers distinguished by a wide range of gas permeability P (1-10⁴ Barrer) and selectivity. They are used therefore as good gas-separating membrane materials.

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