Steve Allman

• AAS, Electronic Engineering
• Research Assistant Retired at Oak Ridge National Laboratory

This work extends a previous percentage level concentration study of the optical emission spectra for six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), along with the transition metal, yttrium (Y) using laser-induced breakdown spectroscopy (LIBS). The concentration of thes...

Separation of ²²⁵Ra (t1/2 = 15 d) from its daughter isotope ²²⁵Ac (t1/2 = 10 d) is necessary to obtain pure ²²⁵Ac for cancer alpha-therapy. In this study, microscale separation of ²²⁵Ra from its daughter ²²⁵Ac using BioRad AG50X4 cation exchange resin was achieved with good reproducibility across microdevices, and ≥90% purity was achieved for ²²⁵Ac...

Laser-induced breakdown spectroscopy (LIBS) was undertaken using an instrument which used a high-powered microscope to deliver the light and tightly focused the low energy laser beam onto the surface of a solid sample. A micro-plasma was generated on the surface of the sample under test even though the amount of energy/pulse from a beam of 532 nm w...

Importance: Plant roots harbor a diverse collection of microbes that live within host tissues. To gain a comprehensive understanding of microbial adaptations to this endophytic lifestyle from strains that cannot be cultivated, it is necessary to separate bacterial cells from the predominance of plant tissue. This study provides a valuable approach...

Building envelope, such as a roof, is the interface between a building structure and the environment. Understanding of the physics of microbial interactions with the building envelope is limited. In addition to the natural weathering, microorganisms and airborne particulate matter that attach to a cool roof tend to reduce the roof reflectance over...

A vapor particle separator including a temperature controlled chamber for desorbing vapors from the particulates of an exhaust gas and a separation chamber including a micro porous membrane. The micro porous membrane provides an interface between at least one particle passageway and at least one vapor passageway through the separation chamber. The...

Despite a long history of investigation, many bacteria associated with the human oral cavity have yet to be cultured. Studies that correlate the presence or abundance of uncultured species with oral health or disease highlight the importance of these community members. Thus, we sequenced several single-cell genomic amplicons from Desulfobulbus and...

Optimization of sample hybridization times. Panel A shows the scatterplot pattern of a Desulfobulbus propionicus culture after 3 (top) or 20 (bottom) hours of hybridization. Panel B shows actual sorting gates for an oral sample after 20 hour hybridization. All images of 528-38 emission (left) were samples hybridized with Alexa488-labeled DELTA495a....

Number of Dsv1 genes with homologs in gut species Desulfovibrio sp. 3_1_syn3, D. piger or environmental species D. vulgaris Hildenborough. The search for homologous genes was performed in IMG [85] with increasing minimum percent identity requirements. A total of 2890 Dsv1 genes were analyzed. (PDF)

Map of enzymes used in propionate metabolism and the methylmalonyl pathway. Genes found in Dsb1-5 (based on E.C. number) are shown in blue. Genes in Desulfobulbus propionicus are shown in red. (EPS)

Maximum likelihood tree of putative srfB genes. The tree was constructed using PHYML [86] in the program Geneious® Pro 5.6.5 with a JTT (+ gamma+invariant sites) substitution model. Predicted proteins from host-associated Deltaproteobacteria are denoted by a blue box. The scale bar indicates 0.3 substitutions per nucleotide position. Numbers given...

Maximum likelihood tree of putative srfC genes. The tree was constructed using PHYML [86] in the program Geneious® Pro 5.6.5 with a JTT (+ gamma+invariant sites) substitution model. Predicted proteins from host-associated Deltaproteobacteria are denoted by a blue box. The scale bar indicates 0.8 substitutions per nucleotide position. Numbers given...

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Flow cytometry (FCM) techniques have been developed for sorting mesophilic organisms, but the difficulty increases if the target microbes are thermophilic anaerobes. We demonstrate a reliable, high-throughput method of screening thermophilic anaerobic organisms using FCM and 96-well plates for growth on biomass-relevant substrates. The method was t...

Laser-induced breakdown spectroscopy (LIBS) has been used to determine the limits of detection of strontium (Sr) and cesium (Cs), common nuclear fission products. Additionally, detection limits were determined for cerium (Ce), often used as a surrogate for radioactive plutonium in laboratory studies. Results were obtained using a laboratory instrum...

Sampling and measurement of volatile particles is a challenging task. It has been hampered by lack of a reliable technique capable of accurately capturing the phase-partition process of the pollutants without generating bias and artifacts in the data. The objective of this research is to design a new vapor-particle separation technique for performi...

This paper investigates the determination of the concentration of a chemical vapor as a function of several nonspecific microcantilever array sensors. The nerve agent dimethyl methyl phosphonate (DMMP) in parts-per-billion concentrations in binary and ternary mixtures is able to be resolved when present in a mixture containing parts-per-million con...

A novel, obligately anaerobic, extremely thermophilic, cellulolytic bacterium, designated OB47T, was isolated from Obsidian Pool, Yellowstone National Park, WY. The isolate was a nonmotile, non-spore-forming, Gram-positive rod approximately 2 μm long by 0.2 μm wide and grew at temperatures between 55 and 85°C, with the optimum at 78°C. The pH range...

Project Goals: The BioEnergy Science Center (BESC) is focused on the fundamental understanding and elimination of biomass recalcitrance. BESC's approach to improve accessibility to the sugars within biomass involves 1) designing plant cell walls for rapid deconstruction and 2) developing multitalented microbes for converting plant biomass into biof...

The development and refinement of a microfluidic-based alginate bead generator system for bacterial encapsulation is presented. The resulting microgels have application for the encapsulation of single cells, and can allow for small scale, clonal expansion of thousands of isolated cells in parallel. PDMS based microfluidic chips were fabricated usin...

We report the experimental details on the successful application of the electronic nose approach to identify and quantify components in ternary vapor mixtures. Preliminary results have recently been presented [L. A. Pinnaduwage etal, Appl. Phys. Lett. 91, 044105 (2007)]. Our microelectromechanical-system-based electronic nose is composed of a micro...

The authors report the identification and quantification of the components of a ternary vapor mixture using a microcantilever-based electronic nose. An artificial neural network was used for pattern recognition. Dimethyl methyl phosphonate vapor in ppb concentrations and water and ethanol vapors in ppm concentrations were quantitatively identified...

A major research effort has been devoted over the years for the development of chemical sensors for the detection of chemical and explosive vapors. However, the deployment of such chemical sensors will require the use of multiple sensors (probably tens of sensors) in a sensor package to achieve selective detection. In order to keep the overall dete...

The 5'-3' exonuclease activity of DNA polymerase was utilized in the polymerase chain reaction system to generate a specific signal concomitant with amplification. These signals were detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). This method obviates the need to perform extensive DNA purifica...

Fragmentation of synthetic oligonucleotides under the influence of biotin was investigated using 3-hydroxypicolinic acid (3-HPA) as a matrix-assisted laser desorption/ionization (MALDI) matrix. Addition of biotin into the sample enhanced fragmentation of the oligonucleotide between bases. However, when the biotin was tagged to the 5'-terminus of th...

Batches of water-soluble gold nanoclusters of nominal 2.0 or 3.5-nm diameter were prepared to evaluate particle size determinations by a number of techniques such as transmission electron microscopy or atomic force microscopy and to validate estimates derived by mass spectrometric analysis using matrix-assisted laser desorption ionization (MALDI)....

During the past few years, we developed and used laser desorption mass spectrometry for biomolecule detections. Matrix-assisted laser desorption/ionization (MALDI) was successfully used to detect DNA fragments with the size larger than 3000 base pairs. It was also successfully used to sequence DNA with both enzymatic and chemical degradation metho...

Two new approaches for nucleic acid hybridizations by MALDI-TOF mass spectrometry are described. Hybridization using genomic DNA without polymerase chain reaction was demonstrated. Total genomic DNA of bacteriophages bound to charge-modified nylon membranes was identified by the hybridization of species-specific oligonucleotide probes. lambda-Phage...

Oligonucleotide ions have been detected using matrix-assisted laser desorption/ionization (MALDI) under nonresonant laser irradiation of the sample. When mass resolution was not limited by adduct attachment to the analyte ions, the nonresonant MALDI spectra demonstrated better resolution than the spectra acquired with resonant ultraviolet irradiati...

A rapid, simple, and reliable gender determination of human DNA samples was successfully obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Detection sensitivity reached 0.01 ng or less for DNA samples.

In this paper, we report for the first time use of laser desorption mass spectrometry for measurement of chemical cleavage sequencing products of DNA. In this method, the target DNA was labeled with biotin and subjected to chemical modification and cleavage according to the Maxam-Gilbert sequencing protocol. The biotin-containing fragments were cap...

Laser desorption mass spectrometry (LDMS) has been developed for DNA sequencing, disease diagnosis, and DNA fingerprinting for forensic applications. With LDMS, the speed of DNA analysis can be much faster than conventional gel electrophoresis. No dye or radioactive tagging to DNA segments for detection is needed. LDMS is emerging as a new alternat...

Genotyping of the dentatorubral-pallidoluysian atrophy (DRPLA) locus in six patient samples, representing four normal individuals and two DRPLA patients, was successfully obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). DRPLA is a dominantly inherited neurodegenerative disorder associated w...

A method has been developed for direct counting of noble gas atoms and has been demonstrated for selected isotopes of krypton. In principle, a few atoms of the noble gases argon, krypton, xenon and radon can now be counted with isotopic selectivity whether stable or radioactive. A concept was originated in which a laser method would be used to coun...

Sequencing of DNA fragments of 130 and 200 bp using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for DNA ladder detection was demonstrated. With further improvement in mass resolution and detection sensitivity, mass spectrometry shows great promise for routine DNA sequencing in the future.

Matrix-assisted laser desorption/ionization was used for the detection of four base short tandem repeats (STR) for clinical samples using a time-of-flight mass spectrometer. Since STR plays an important role in genetic disease and human identification, this work indicates that laser desorption mass spectrometry has the potential to achieve rapid DN...

The basic principles and experimental results of laser-induced acoustic desorption (LIAD) are reported in this work. LIAD was successfully used to desorb biomolecules in a mass spectrometer. LIAD holds some promise to eliminate many key factors which contribute to poor mass resolution in MALDI. Thus, it has potential for improvement in resolution o...

Laser irradiation of absorbing materials can be used to generate acoustic pulses with extremely high amplitude and short pulse duration. Such acoustic pulses can transfer energy and momentum to atomic particles on solid surfaces to cause desorption of the particles. We report experimental observations of the effect of laser-induced acoustic desorpt...

Oligonucleotide sequencing by fragmentation in matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry has been demonstrated. With this sequencing method, the preparation of oligonucleotide ladder products and gel electrophoresis are not required, thus the sequencing speed potentially can be increased. Sequence info...

Since laser mass spectrometry has the potential for achieving very fast DNA analysis, we recently applied it to DNA sequencing, DNA typing for fingerprinting, and DNA screening for disease diagnosis. Two different approaches for sequencing DNA have been successfully demonstrated. One is to sequence DNA with DNA ladders produced from Sanger's enzyma...

The DNA sequence of a single-stranded and double-stranded template was determined. The templates were sequenced using the chain termination method and cycle sequencing method and detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The sequencing products were analyzed successfully without the laborious and expe...

The DNA sequence of a single-stranded and double-stranded template was determined. The templates were sequenced using the chain termination method and cycle sequencing method and detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The sequencing products were analyzed successfully without the laborious and expe...

A point mutation can be associated with the pathogenesis of inherited or acquired diseases. Laser desorption mass spectrometry coupled with allele specific polymerase chain reaction (PCR) was first used for point mutation detection. G551D is one of several mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene present in 1...

The effect of ammonium salt in the detection of oligonucleotides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been systematically investigated using several matrices with ammonium salt additives. The results show that the presence of ammonium salt in the matrix has a beneficial effect on protonation and deprot...

Summary form only given. In order to use mass spectrometry for fast DNA sequencing, there are three requirements: (1) detection of large DNA segments, (2) detection sensitivity in the femtomole region, and (3) resolution must be good enough to resolve DNA sizes of one nucleotide difference. With pulsed ion extraction, mass resolution of more than 1...

Laser desorption mass spectrometry has been used for molecular diagnosis of cystic fibrosis. Both 3-base deletion and single-base point mutation have been successfully detected by clinical samples. This new detection method can possibly speed up the diagnosis by one order of magnitude in the future. It may become a new biotechnology technique for p...

The matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometric study of DNA detection using 2,3,4-trihydroxyacetophenone, 2,4,6-trihydroxyacetophenone, and their combination has been carried out systematically. The results show that a mixture of 2,4,6-trihydroxyacetophenone, 2,3,4-trihydroxyacetophenone and ammonium citra...

The 3p ← n Rydberg transitions of acetone(CH3COCH3) and deuterium acetone(CD3COCD3) have been carefully investigated using mass resolved two-photon resonant ionization spectroscopy with a jet-cooled molecular beam utilizing linear and circular polarized light. The symmetry of 3p acetone vibronic states have been reanalyzed. The experimental results...

Matrix-assisted laser desorption/ionization (MALDI) has been pursued for fast DNA analysis and sequencing. In this article, recent progress on detecting large oligonucleotides is reviewed. The potential application of MALDI for population screening for disease diagnosis is discussed. The approach of using MALDI for DNA sequencing is presented. Disc...

The matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometric study of DNA detection using 2,3,4-trihydroxyacetophenone, 2,4,6-trihydroxyacetophenone, and their combination has been carried out systematically. The results show that a mixture of 2,4,6-trihydroxyacetophenone, 2,3,4-trihydroxyacetophenone and ammonium citra...

The effect of ammonium salt in the detection of oligonucleotides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry has been systematically investigated using several matrices with ammonium salt additives. The results show that the presence of ammonium salt in the matrix has a beneficial effect on protonation and deprot...

During the past few years, major effort has been directed toward developing mass spectrometry to measure biopolymers because of the great potential benefit to biomedical research. Hellenkamp and his co-workers were the first to report that large polypeptide molecules can be ionized and detected without significant fragmentation when a greater numbe...

Laser desorption mass spectrometry has been considered as a potential new method for fast DNA sequencing. Our approach is to use matrix-assisted laser desorption to produce parent ions of DNA segments and a time-of-flight mass spectrometer to identify the sizes of DNA segments. Thus, the approach is similar to gel electrophoresis sequencing using S...

The absorption of laser energy by recently found matrices used in matrix assisted laser desorption ionization (MALDI) detection of large DNA segments: 3-hydroxypicolinic acid (3-HPA), picolinic acid (PA), composite matrix (PA + 3-HPA) and 3-aminopicolinic acid (3-APA), was studied by using a fast piezoelectric transducer for solid matrices and for...

Matrix-assisted laser desorption/ionization (MALDI) was used for several small proteins (such as insulin) and for peptides. It was found that the detection efficiencies of MALDI for the insulin B chain and the insulin A chain are drastically different. Similar phenomena were also observed for various types of peptides. The positive-ion signal of MA...

The most common mutation of the cystic fibrosis gene is characterized by the deletion of three nucleotides that code phenylalanine in the 508 position of the cystic fibrosis transmembrane conductance regulator. We report the first measurements by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry for the delta F508...

Fast DNAsequencing by laser mass spectrometry is possible if the following 3 criteria are met: (1) Size of DNA fragment should be greater than 300 nucleotides. (2) Enough sensitivity to detect DNA produce from polymerases chain reactins (PCR). (3) Higher resolution of mass spectr. So far, the firt 2 criteria are met: If the resolution can be signif...

3-Aminopicolinic acid (3-APA) was tested and found to be a useful matrix for matrix-assisted laser desorption/ionization of DNA and protein. Single-stranded DNA segments of 150-mer and double-stranded DNA of 246 base pairs were successfully detected by using 3-APA as an ultraviolet-absorbing matrix in a linear time-of-flight mass spectrometer. In t...

The application of DNA fingerprinting has become very broad in forensic analysis, patient identification, diagnostic medicine, and wildlife poaching, since every individual's DNA structure is identical within all tissues oftheir body. DNA fingerprinting was initiated by the use of restriction fragment length polymorphisms (RFLP). In 1987, Nakamura...

We found that picolinic acid is a very good matrix for matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry of oligonucleotides, proteins and tRNA. Among the oligonucleotides, picolinic acid was shown to be effective for homo-oligonucleotides, d(G)40 and d(C)60, and for mixed-base oligonucleotides up to 190 bases. In...

We report the first detection of DNA segments as large as 500 nucleotides by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, using picolinic acid and 3-hydroxypicolinic acid mixtures as desorption matrices. The successful detection of 500-nucleotide DNA indicates that laser mass spectrometry is now emerging as a new biotechno...

Hyperfine structure plays a major role in producing “anomalous” odd-to-even isotope ratios in the stepwise excitation, ionization and mass analysis of an element with broad bandwidth, long-pulsed lasers. PAYNE et al. [Spectrochim Acta46B, 1439 (1992)] proposed that these anomalies may be avoided by cautious application of a simple prescription. We...

The Rydberg states of the acetylene clusters (C2H2)2 and (C2H2)3 have been resolved by the technique of two-photon resonant ionization spectroscopy in the energy region of the monomer gerade Rydberg states. The stability of these cluster Rydberg states has been found to be vibrational mode dependent. The geometry of the clusters, and the mechanism...

Apparatus for detecting an electronegative species comprises an analysis chamber, an inlet communicating with the analysis chamber for admitting a sample containing the electronegative species and an ionizable component, a radioactive source within the analysis chamber for emitting radioactive energy for ionizing a component of the sample, a propor...

Matrix-assisted laser desorption/ionization, by a time-of-flight mass spectrometer, has been successfully used for detection of restriction enzyme-digested DNA. However, the oligonucleotide segments detected correspond to the molecular weights of single strands.

Apparatus for detecting an electronegative species comprises an analysis chamber, an inlet communicating with the analysis chamber for admitting a sample containing the electronegative species and an ionizable component, a radioactive source within the analysis chamber for emitting radioactive energy for ionizing a component of the sample, a propor...

Since the discovery that chlorofluorocarbons (CFCs) destroy the ozone layer, the need to reduce the release of these refrigerants into the environment has become critical. A total ban of ozone-depleting CFCs is expected within a few years, and hydrofluorocarbons (HFCs) and fluorocarbons (FCs) and their mixtures are expected to be used during a tran...

Various matrix materials were used for laser desorption of biological molecules, which include proteins and oligonucleotides. Both matrix-assisted laser desorption ionization (MALDI) and matrix-assisted laser desorption with post-ionization (MALPI) have been tried. Detection sensitivity of a few hundred femtomoles has been achieved by MALDI for oli...

Ferulic acid, 3-hydroxypicolinic acid (3-HPA), and 2,5-dihydroxybenzoic acid (2,5-DHB) were used as matrices in MALDI of various oligonucleotides. It was found that 2,5-DHB is an excellent matrix for polydeoxyribothymidylic acid. A poly-T oligonucleotide with a size of 130 bases was successfully detected. 3-HPA was found to be a good matrix for MAL...

Negative ions of small oligonucleotides are shown to undergo collisional and collision-free neutralization following matrix assisted laser desorption and ionization (MALDI). Using a modified MALDI time of flight instrument, approximate collisional cross sections and collision-free lifetimes have been measured for negative ions of 3-, 4-, 6- and 7-m...

During the past few years, major efforts have been made to use mass spectrometry to measure biopolymers because of the great potential benefit to biological and medical research. Although the theoretical details of laser desorption and ionization mechanisms of MALDI are not yet fully understood, several models have been presented to explain the pro...

Various isomer matrices were used for laser-desorption ionization of mixtures of oligomers. It was found that the efficiency of production of oligomer ions changed drastically when different isomers were used as matrices. For selected matrix materials, parent oligomer ions with sizes up to 64 bases were observed.

During the past few years, tremendous effort has been put to achieving fast sequencing of DNA due to the potential great applications in biological and medical research. Current successful DNA sequencing methods which were developed by Sanger and Maxam-Gilbert have proven very useful for sequencing small DNA segments. However, these methods of sequ...

Matrix-assisted laser desorption/ionization mass spectrometry has been used to mass analyze synthetic oligomers of poly-T ranging in size from 20 to 100 nucleotides. Both positively- and negatively-charged parent molecular ions were observed.

A method for analyzing a gaseous electronegative species comprises the steps of providing an analysis chamber; providing an electric field of known potential within the analysis chamber; admitting into the analysis chamber a gaseous sample containing the gaseous electronegative species; providing a pulse of free electrons within the electric field...

During the past few years, researchers at ORNL have developed the following new instruments involving the use of a laser for environmental and biotechnology research: (1) a single atom detector; (2) a rare gas atom counter; (3) a biopolymer mass spectrometer; and (4) a vacuum ultraviolet (VUV) ionizer mass spectrometer. Their basic principles and a...

Various matrices were used for laser-desorption ionization of mixtures of small DNA segments. Parent negative ions of 34-mer as well as other smaller single-stranded oligomers were observed for selected organic acids and dye compounds. Both positive and negative parent ions were observed with very little fragmentation. Effects of various matrices a...

It has been shown that hyperfine structure plays a major role in producing anomalous'' odd to even isotope ratios in the step wise excitation and ionization of an element with broad bandwidth lasers. This investigation is based on the suggestion that isotope biases may be avoided by detuning the laser from resonance by an amount greater than either...

It has recently been shown that in the stepwise excitation and ionization of an element with broad bandwidth lasers, there are major effects due to the fact that even and odd isotopes have different hyperfine structures. The increase in the number of levels and the decrease in the dipole matrix elements of the individual transitions leads to easily...

This volume focuses on the fundamentals of the technique of analysing material based on the atomic weight of the species, using the power and definition of lasers to enable measurement of smaller quantities and more finely localized particles. Each chapter deals with a particular application area and should be sufficient to form an entry point for...

Vacuum ultraviolet light in the range 116 nm to 117 nm was produced by using a two-photon resonant four-wave mixing scheme in Xe. The buildup of coherent cancellation of the two-photon resonant transition employed in the generation of the vacuum ultraviolet, with resulting limitations imposed on the achievable vacuum ultraviolet intensity was inves...

Method and apparatus for determining small quantities of specific atoms with isotopic selectivity.

A new analytical technique based on resonant ionization of krypton with a vacuum ultraviolet (VUV) laser source was used to determine low-level 81Kr concentrations in groundwater. The long half-life (210000 yr) and low concentration (1.3 × 10381Kr atoms per liter of modern water at 10°C) make the detection of 81Kr by radioactive counting techniques...

It has now been show that it is feasible to measure the 7Be neutrino source in the sun by using the reaction 8 1Br(ν,e−)8 1Kr in a radiochemical experiment. Such an experiment would be quite similar to the Davis, Cleveland, and Rowley method for measuring the 8B neutrino using 3 7Cl(ν,e−)3 7Ar except that the resonance ionization spectroscopy (RIS...

A new laser-based analytical technique is described for isotope selective noble gas atom counting. The method has been used to detect /sup 81/Kr atoms in a groundwater sample. 2 refs., 4 figs.

A new analytical technique with sufficient sensitivity to determine 81Kr concentrations in groundwater is described. The method utilizes single-atom counting by laser resonance ionization spectroscopy (RIS) in combination with a small spectrometer to achieve the required selectivity and sensitivity. A first demonstration of the technique for ground...

The standard stellar model of the sun, that of BAHCALL [1], predicts the neutrino flux and energy spectrum emitted by the hot interior core where energy production occurs. It is believed that neutrinos provide the only means of observing the thermonuclear region of the sun. An experiment by DAVIS et al. [2] to measure the flux due to one of the hig...

A new analytical technique based on resonant ionization of krypton with a vacuum ultraviolet (VUV) laser source was used to determine low-level ⁸¹ Kr concentrations in groundwater. The long half-life (210,000 yr) and low concentration (1.3 × 10 3 81 Kr atoms/liter of modern water) make the detection of ⁸¹ Kr by radioactive counting techniques extre...

A resonance ionization ion source, in conjunction with a mass spectrometer, was used to count 1000 individual 81Kr atoms. In this method, a vacuum ultraviolet beam was used to resonantly excite krypton atoms in order to obtain atomic species selectivity and a small quadrupole mass spectrometer provided isotopic selectivity. After selection, the kry...

Resonance ionization spectroscopy (RIS) was used to count 1000 individual ⁸¹Kr atoms. In the method, lasers for RIS are used to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. After Z and A selection the krypton ions were counted as they were implanted into a ta...

Radioactive ⁸⁵Kr was used in a closed volume under moderate vacuum to investigate mechanisms by which inert gas atoms are pumped in an electron‐impact ionization source of a simple diode design. Results are consistent with a mechanism involving the conversion of inert gas ions into energetic neutrals at the cathode followed by...

Five different fluctuation phenomena at the atomic and molecular levels have been studied by resonance ionization spectroscopy techniques with one-atom detection sensitivity. The Poisson distribution described the observed frequency distributions suggesting random behavior. In addition, a gedanken experiment suggested by Einstein and Furth on the d...

The technique of resonance ionization spectroscopy (RIS) was extended to develop a means for counting individual atoms of a selected isotope of a noble gas. The experimental schematic is shown in Fig. 1. The concept for counting noble gas atoms with isotopic selectivity utilizes a laser for ionizing atoms of a selected atomic number (Z) and a mass...

Fluctuation studies of atomic molecular populations have been made by means of one-atom detection techniques. Density fluctuations of atoms and density fluctuations of molecules, as well as photoionization yield, photodissociation yield, and collisional broadening fluctuations, were studied, using appropriate laser saturation conditions. In each ca...