V. A. Raman

R.f. spark source mass spectrometric studies of molecular ions

Abstract The small molecular ions such as the carbides (MC +,2+ n ), oxides (MO +,2+ n ) and some other matrix-sensitive ions in the beam produced from an r.f.-spark ion source have been studied for a number of elements (M) of varying electronic configurations. The MC + n ions of a given element, M, generally follow either of the following two yield distribution patterns, namely, (i) a monotonic decrease in the MC + n ion yield as n increases and (ii) a zigzag abundance distribution with the peaks appearing at even n values. The oxide ions, MO + n , due to any given element (M) show only the decreasing trend in yields with n and the higher oxides ( n ⩾ 3) are generally rare. The other molecules, some of which are metal or matrix-sensitive and which may be of concern for elemental analysis, include metal hydride (MH), hydroxide (MOH), halide (MX), cyanide (MCN), polymeric species such as M n , M m C n , M m O n , M m O n H p , M m X n , etc. The studies show that, unless the nature of the molecular mass spectrum for a given matrix is predetermined, the elemental analysis may turn out to be erroneous. Factors governing the abundance of molecules in the recorded ion beam and the probable processes of their formation are discussed.

An experimental evaluation of procedures used for quantitative analysis in RF-spark source mass spectrometry

Abstract The determination of trace constituents in materials of high purity using spark source mass spectrometry normally employs the sensitivity calibration technique. In this technique, either the matrix element is used as reference or certain selected elements known as internal standards are used as reference. The photoplate evaluation procedure adapted for quantitative analysis is a matter of choice from the various procedures available in the literature. Investigations were carried out on the adaptability of these methods and different photoplate evaluation procedures. This paper describes the precision and accuracy achievable, as well as the relative advantages and disadvantages of these methods when the matrix or an element closely resembling the element being determined is used as reference element.

Relative sensitivity factors for the determination of rare earth elements in uranium oxide by Spark Source Mass Spectrometry

ZusammenfassungDie relativen Empfindlichkeitsfaktoren für die Elemente Ce, Nd, Sm, Eu, Gd, Dy, Er und Lu in U3O8 wurden mit der Funken-Massenspektrometrie mit elektrischem Nachweis (peak switching) bestimmt. Früher sind diese Faktoren in Uranylnitrat bestimmt worden und es wurde erwartet, daß trotz unterschiedlicher absoluter Werte der Trend derselbe wäre. Es zeigte sich jedoch, daß auch der Trend verschieden ist. Die Werte der vorliegenden Untersuchung stimmen mit theoretischen Berechnungen aus den Zersetzungsenergien der Seltenerdoxide überein und bestätigen die Ergebnisse anderer Autoren für die Y2O3-Matrix.SummaryRelative Sensitivity Factors (RSFs) for the rare earth elements Ce, Nd, Sm, Eu, Gd, Dy, Er and Lu in U3O8 have been determined by Spark Source Mass Spectrometry (SSMS) using the electrical detection system in peak switching mode. Earlier RSFs for these elements were determined in uranyl nitrate and it was expected that though the absolute value of the RSFs may be different, the trend would be the same. However, the present work shows that apart from the magnitude, the trend in RSF values is also different. The data from the present work are in agreement with the theoretical calculations based on the decomposition energies of the rare earth oxides and support the work carried out by others in the case of Y2O3 matrix.

Determination of zirconium in U−Zr−Al and Pu−Zr−Al alloys by isotope dilution thermal ionization mass spectrometry

An isotope dilution thermal ionization mass-spectrometric (ID-TIMS) method is described for the determination of Zr in U−Zr−Al and Pu−Zr−Al alloy samples. Problems encountered in the chemical exchange between the zirconium isotopes in the spike and sample, particularly Pu−Zr−Al samples, are discussed and a method has been standardized to eliminate it. Separation of Zr from U, Pu and Al was achieved by employing ion exchange procedures. A precision of better than 1% is possible in the determination of Zr with the method reported here.

Determination of Hydrogen in Zircaloy by Spark Source Mass Spectrometry

Abstract Application of Spark Source Mass Spectrometry(SSMS) for the determination of hydrogen in zircaloy clad material used in nuclear reactors is reported. The advantage of SSMS lies in the fact that along with the metallic trace constituents even the nonmetallics including the gaseous impurities can also be determined in a single analysis using the photoplate detection system. The value obtained for H2 using photoplate detection system is compared with that obtained in electrical detection system in SSMS and also with the value obtained employing the conventional inert gas fusion technique.

Determination of trace impurities in zircaloy-2 and tellurium by spark source mass spectrometry

Determination of trace impurities in zircaloy-2 and tellurium by Spark Source Mass Spectrometry (SSMS) is reported. The advantage of SSMS lies in the fact that along with metallic trace constituents even the nonmetallic impurities and gases including hydrogen can also be determined.

Charge distribution of elements in the ion beam produced from an RF-spark ion source

Abstract The ion yield distribution of elements with respect to charge in the beam produced from an rf-spark ion source has been studied for eight matrices. The thermochemical behaviour of the elements as well as the features of the matrix plasma are found to be the key factors. It is shown that the consideration of charge distribution helps to improve the precision of the spark source mass spectrometric analysis. It is argued that, in the course of the development of the matrix plasma, the vaporised particles in the sparking zone undergo element-sensitive multiple ionization. It is further concluded that, during the process of expansion of the plasma into the vacuum, the ions of different elements suffer different rates of recombination. Thus, the ionization energy available per particle controls the charge distribution of the elements in the plasma while the abundances of ions according to charge in the beam are regulated by the average energy available per particle and different recombination rates.

Accuracy in the Isotope Dilution Mass Spectrometry of Uranium in Rubidium Uranium Sulphate Rb2U(SO4)3

Abstract Problems encountered in the determination of uranium in rubidium uranium sulphate (Rb2U(SO4)3) employing isotope dilution thermal ionisation mass spectrometry (ID-TIMS) are discussed. The positive bias of 0.2 to 0.3% in the determination of uranium in Rb2U(SO4)3 by ID-TIMS with respect to the stoichiometric composition has been resolved by modifying the chemical exchange procedures. The concentration of uranium in Rb2U(SO4)3 could be determined with an accuracy better than 0.1% employing the HClO4 treatment for proper isotopic exchange between the spike and sample isotopes.

Carbon cluster formation in an rf-spark source

Abstract The intensity of carbon clusters in an rf-spark source was investigated in four different matrices. The periodicity of cluster formation in pure graphite could not be significantly observed in other matrices. Also, the abundance of lower clusters C 2 + and C 3 + was found to depend on the mass number of the major element present in the matrix. Interpretation of these results led to the consideration of sputtering of the electrode material by ion bombardment as a possible mechanism for cluster formation followed by their redistribution in the vapour phase through an irreversible momentum transfer resulting in larger abundance of lower clusters.

Degradation of the mass spectrum due to reflected ions in spark source mass spectrometry employing an electrical detection system

Abstract The experience of using an electrical detection system in spark source mass spectrometry, with particular reference to the presence of diffuse peaks at the mass numbers of interest, is reported. A possible solution to the problem of these diffuse peaks is also reported.