Frequency scan for the analysis of high mass ions generated by matrix-assisted laser desorption/ionization in a paul trap

An ion trap has been modified for the analysis of high mass ions generated by matrix-assisted laser desorption/ionization. Samples are deposited on a probe tip and introduced directly onto the hyperbolically shaped surface of one endcap. All three electrodes - both the endcaps and the ring electrode - are insulated so that the radio frequency (Rf) voltage may be applied to the center ring electrode and the inverted Rf voltage to the endcaps. By using low frequencies (below 100 kHz) and low amplitudes (below 200 V), high mass singly charged ions may be trapped and analyzed by a frequency sweep at constant amplitude. In the high mass range (60-160 kDa), this instrument showed good sensitivity, signal-to-noise ratios, and mass resolution. Copyright 1999 John Wiley & Sons, Ltd.     

Nanolithography with metastable helium atoms in a high-power standing-wave light field

We have created periodic nanoscale structures in a gold substrate with a lithography process using metastable triplet helium atoms that damage a hydrophobic resist layer on top of the substrate. A beam of metastable helium atoms is transversely collimated and guided through an intense standing-wave light field. Compared to commonly used low-power optical masks, a high-power light field (saturation parameter of 10⁷) increases the confinement of the atoms in the standing wave considerably, and makes the alignment of the experimental setup less critical. Due to the high internal energy of the metastable helium atoms (20 eV), a dose of only one atom per resist molecule is required. With an exposure time of only eight minutes, parallel lines with a separation of 542 nm and a width of 100 nm (one-eleventh of the wavelength used for the optical mask) are created.PACS 32.80.Lg; 39.25.+k; 81.16.Nd     

Numerical simulations on the motion of atoms travelling through a standing-wave light field

The motion of metastable helium atoms travelling through a standing light wave is investigated with a semi-classical numerical model. The results of a calculation including the velocity dependence of the dipole force are compared with those of the commonly used approach, which assumes a conservative dipole force. The comparison is made for two atom guiding regimes that can be used for the production of nanostructure arrays; a low power regime, where the atoms are focused in a standing wave by the dipole force, and a higher power regime, in which the atoms channel along the potential minima of the light field. In the low power regime the differences between the two models are negligible and both models show that, for lithography purposes, pattern widths of 150 nm can be achieved. In the high power channelling regime the conservative force model, predicting 100 nm features, is shown to break down. The model that incorporates velocity dependence, resulting in a structure size of 40 nm, remains valid, as demonstrated by a comparison with quantum Monte-Carlo wavefunction calculations.Received: 11 December 2002, Published online: 29 July 2003PACS: 02.60.Cb Numerical simulation; solution of equations - 32.80.Lg Mechanical effects of light on atoms, molecules, and ions - 81.16.Rf Nanoscale pattern formationL. Feenstra: Present address: Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany.     

Spontaneous formation of indium-rich nanostructures on InGaN(0001) surfaces

We show how a nonlinear system that supports solitons can be driven to generate exact (regular) Cantor set fractals. As an example, we use numerical simulations to demonstrate the formation of Cantor set fractals by temporal optical solitons. This fractal formation occurs in a cascade of nonlinear optical fibers through the dynamical evolution from a single input soliton.     

Nuclear spectroscopy of neutron-richA=145 nuclei

A study of theβ-decay of neutron-richA=145 fission products was undertaken by the use of the two recoil separators LOHENGRIN and JOSEF and the ISOL-type separator OSTIS. Theβ-decaying isotopes¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce were extensively studied. Level schemes for¹⁴⁵La,¹⁴⁵Ce and¹⁴⁵Pr were deduced fromγ and conversion electron spectra,γγ, X γ delayed andβγ coincidences. TheQ _β -values have been measured for the¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce decays.     

Average multipolarities of quasi-continuum transitions following the (α, 4n) reaction from measured internal conversion coefficients

The quasi-continuum of electromagnetic transitions following the ¹⁶⁰Gd(α,4n)¹⁶⁰Dy reaction exhibits predominant E1 character. This is condluded from conversion electrons observed with a mini-orange spectrometer and corresponding γ-rays, both being selected by coincidences with discrete ground-state band transitions in ¹⁶⁰Dy.     

Abrasion measurements by radiotracers. Application to the spatial distribution of trace elements in flameless AAS

A simple abrasion procedure for the determination of the distribution of a radiotracer as a function of depth in solid flat aliquots is presented. Application to the concentration distribution in graphite furnaces for flameless AAS is possible down to 0.1 m.     

Microwave absorption studies of MgB2 superconductor

Microwave absorption studies have been carried out on MgB₂ superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10 μm) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a ✓H dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.     

The FT-IR study of the brain tissue of Labeo rohita due to arsenic intoxication

The brain is believed to be particularly vulnerable to arsenic due to its high oxygen consumption rate and high level of polyunsaturated fatty acids and relatively high rate of oxygen free radical generate without commensurable level of arsenic. Hence, in the present work an attempt is made to study the changes in the biochemical contents in the brain tissues of edible fish Labeo rohita due to arsenic intoxication using Fourier Transform Infrared (FT-IR) spectroscopy. FT-IR spectra reveal significant differences in absorbance intensities between the control and arsenic intoxicated brain tissues, reflecting an alteration on the major biochemical constituents, such as lipids, proteins and nucleic acids of the brain tissues of L. rohita due to arsenic intoxication. Further, the administration of antidote DMSA improves the protein and lipid contents significantly in the brain tissues when compared to arsenic intoxicated tissues. The decrease in α-helix structure due to arsenic intoxication might be responsible for the increase in β-sheet secondary structures, which is consistent with the mechanism of β-sheet formation.     

Stability of hypobromite solutions

The stability of hypobromite solutions is governed by such factors as the concentration of hypobromite and hydroxide, light, temperature, and the presence of foreign substances. From a review of the literature it is concluded that it is impossible to obtain perfectly stable solutions. The preparation of more or less stable hypobromite solutions is described, and the dependence of the stability on various factors is determined.