Precision Lifetime Measurements Research Articles

Influence of Ionizing Radiation on Spontaneously Formed Aggregates in Proteins or Enzymes Solutions.

We have shown that many proteins and enzymes (ovalbumin, β-lactoglobulin, lysozyme, insulin, histone, papain) undergo concentration-dependent reversible aggregation as a result of the interaction of the studied biomolecules. Moreover, irradiation of those protein or enzyme solutions under oxidative stress conditions results in the formation of stable soluble protein aggregates. We assume that protein dimers are mainly formed. A pulse radiolysis study has been made to investigate the early stages of protein oxidation by N3• or •OH radicals. Reactions of the N3• radical with the studied proteins lead to the generation of aggregates stabilized by covalent bonds between tyrosine residues. The high reactivity of the •OH with amino acids contained within proteins is responsible for the formation of various covalent bonds (including C-C or C-O-C) between adjacent protein molecules. In the analysis of the formation of protein aggregates, intramolecular electron transfer from the tyrosine moiety to Trp• radical should be taken into account. Steady-state spectroscopic measurements with a detection of emission and absorbance, together with measurements of the dynamic scattering of laser light, made it possible to characterize the obtained aggregates. The identification of protein nanostructures generated by ionizing radiation using spectroscopic methods is difficult due to the spontaneous formation of protein aggregates before irradiation. The commonly used fluorescence detection of dityrosyl cross-linking (DT) as a marker of protein modification under the influence of ionizing radiation requires modification in the case of the tested objects. A precise photochemical lifetime measurement of the excited states of radiation-generated aggregates is useful in characterizing their structure. Resonance light scattering (RLS) has proven to be an extremely sensitive and useful technique to detect protein aggregates.

Interplay between nuclear chiral and reflection symmetry breakings revealed by the lifetime measurements in 76Br

Nearly degenerate positive-parity doublet bands and several E1 transitions between positive- and negative-parity bands have been identified in 76Br. These experimental observations are interpreted as the coexistence of chirality and octupole correlations, based on the analysis of detailed γ-ray spectroscopy with the precise lifetime measurements and theoretical calculations, and play a key role to explore the simultaneous breaking of chiral and reflection symmetry and their interplay. The present work provides the first test for chirality in the A≈80 mass region by lifetime measurements, and firstly elucidates the formation of chiral geometry in the presence of the octupole correlations in Br isotopes, leading to the conclusion that the reflection symmetry breaking catalyzes rather than destroys chiral symmetry breaking in nuclear systems.

High-resolution energy and fast timing measurements for nuclear spectroscopy using digital signal processing

Simultaneous high-resolution energy and picosecond timing measurements have been established with an 8-channel, 14-bit, 500 MS/s digitizer coupled to semiconductor and scintillation radiation detectors, resulting in performance equivalent to that obtained with analog electronics. By interpolating between the 2 nanosecond time stamps associated with the sampling frequency, timing up to few tens of picoseconds is achieved. Energy resolution and linearity are determined to be excellent. Coincidence and precise lifetime measurements performed indicate the utility in complex gamma-ray spectroscopic studies.

π0 decay precision-tests the chiral anomaly.

More precise neutral pion lifetime measurements probe quantum symmetry breaking

High-precision calculations of the 1s22s2p P11→1s22s2 S01 spin-allowed E1 transition in C iii

Large-scale relativistic calculations are performed for the transition energy and line strength of the $ 1s^{2} 2s 2p$ $^1P_{1} \,-\ 1s^{2} 2s^{2}$ $^1S_{0} $ transition in Be-like carbon. Based on the multiconfiguration Dirac-Hartree-Fock~(MCDHF) approach, different correlation models are developed to account for all major electron-electron correlation contributions. These correlation models are tested with various sets of the initial and the final state wave functions. The uncertainty of the predicted line strength due to missing correlation effects is estimated from the differences between the results obtained with those models. The finite nuclear mass effect is accurately calculated taking into account the energy, wave functions as well as operator contributions. As a result, a reliable theoretical benchmark of the $E1$ line strength is provided to support high precision lifetime measurement of the $ 1s^{2} 2s 2p$ $^1P_{1} $ state in Be-like carbon.

New project for precise neutron lifetime measurement at J-PARC

The decay lifetime of free neutrons (∼880 s) is an important parameter of the weak interaction and for Big Bang Nucleosynthesis. However, results of measurements currently show discrepancies depending on the method used. As most experiments nowadays employ ultra cold neutrons, we have developed a new cold-beam experiment which we perform at the Japan Proton Accelerator Research Complex. As a special feature, a polarized neutron beam is bunched by a spin flip chopper. A time projection chamber operated with He and CO2gas, including a well-controlled amount of3He, is used for detection of the beta-decays and simultaneous determination of the beam intensity. Using the data between 2014 and 2016, we evaluated our first, preliminary result of the neutron lifetime as 896 ± 10(stat.)−10+14(sys.) s. We plan several upgrades to achieve our precision goal of 1 s.

Doppler-shift attenuation lifetime measurement of the Ar3621+ level

At TRIUMF, the TIGRESS Integrated Plunger device and its suite of ancillary detector systems have been implemented for charged-particle tagging and light-ion identification in coincidence with γ-ray spectroscopy for Doppler-shift lifetime studies and low-energy Coulomb excitation measurements. As a test of the device, the lifetime of the first 2+ excited state in Ar36 was measured from the γ-ray line shape of the 21+→0g.s.+ transition using the Doppler-shift attenuation technique following Coulomb excitation. The line-shape signatures, vital for precision lifetime measurements, were significantly improved by enhanced reaction-channel selectivity using a complementary approach of kinematic gating and digital rise-time discrimination of recoiling charged particles in a silicon PIN diode array. The lifetime was determined by comparisons between the data and simulated line shapes generated using our TIGRESS Coulomb excitation code as an input to the Lindhard method, which was then extended and included as a class in geant4. The model-independent lifetime result of 490±50 fs corresponds to a reduced quadrupole transition strength of B(E2;21+→0g.s.+)=56±6e2fm4 and agrees well with previous intermediate energy Coulomb excitation measurements, thereby resolving reported discrepancies in the 21+ level lifetime in this self-conjugate nucleus.5 MoreReceived 13 April 2017Revised 28 June 2017DOI:https://doi.org/10.1103/PhysRevC.96.024305©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsLifetimes & widthsNuclear structure & decaysProperties20 ≤ A ≤ 38TechniquesRadiation detectorsShell modelNuclear Physics

Recoil distance method lifetime measurement of the 21+ state in Sr94 and implications for the structure of neutron-rich Sr isotopes

A high precision lifetime measurement of the ${2}_{1}^{+}$ state in $^{94}\mathrm{Sr}$ was performed at TRIUMF's ISAC-II facility by coupling the recoil distance method implemented via the TIGRESS integrated plunger with unsafe Coulomb excitation in inverse kinematics. Due to limited statistics imposed by the use of a radioactive $^{94}\mathrm{Sr}$ beam, a likelihood ratio ${\ensuremath{\chi}}^{2}$ method was derived and used to compare experimental data to Geant4 simulations. The $B(E2;{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ value extracted from the lifetime measurement of $7.{80}_{\ensuremath{-}0.40}^{+0.50}\text{(stat.)}\ifmmode\pm\else\textpm\fi{}0.07\text{(sys.)}$ ps is approximately 25% larger than previously reported while the relative error has been reduced by a factor of approximately 8. A baseline deformation has been established for Sr isotopes with $N\ensuremath{\le}58$ which is a necessary condition for the quantum phase transition interpretation of the onset of deformation in this region. A comparison to existing theoretical models is presented.

Age Related Assessment of Sugar and Protein Intake of Ceratitis capitata in ad libitum Conditions and Modeling Its Relation to Reproduction.

In the inquiry on the age related dietary assessment of an organism, knowledge of the distributional patterns of food intake throughout the entire life span is very important, however, age related nutritional studies often lack robust feeding quantification methods due to their limitations in obtaining short-term food-intake measurements. In this study, we developed and standardized a capillary method allowing precise life-time measurements of food consumption by individual adult medflies, Ceratitis capitata (Diptera: Tephritidae), under laboratory conditions. Protein or sugar solutions were offered via capillaries to individual adults for a 5 h interval daily and their consumption was measured, while individuals had lifetime ad libitum access to sugar or protein, respectively, in solid form. Daily egg production was also measured. The multivariate data-set (i.e., the age-dependent variations in the amount of sugar and protein ingestion and their relation to egg production) was analyzed using event history charts and 3D interpolation models. Maximum sugar intake was recorded early in adult life; afterwards, ingestion progressively dropped. On the other hand, maximum levels of protein intake were observed at mid-ages; consumption during early and late adult ages was kept at constant levels. During the first 30 days of age, type of diet and sex significantly contributed to the observed difference in diet intake while number of laid eggs varied independently. Male and female adult longevity was differentially affected by diet: protein ingestion extended the lifespan, especially, of males. Smooth surface models revealed a significant relationship between the age dependent dietary intake and reproduction. Both sugar and protein related egg-production have a bell-shaped relationship, and the association between protein and egg-production is better described by a 3D Lorenzian function. Additionally, the proposed 3D interpolation models produced good estimates of egg production and diet intake as affected by age, providing us with a reliable multivariate analytical tool to model nutritional trends in insects, and other organisms, and their effect upon life history traits. The modeling also strengthened the knowledge that egg production is closely related to protein consumption, as suggested by the shape of the medfly reproduction-response function and its functional relationship to diet intake and age.

Development of time projection chamber for precise neutron lifetime measurement using pulsed cold neutron beams

A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with 6Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.

Measurements of the B +, B 0, $ B_s^0 $ meson and $ \Lambda_b^0 $ baryon lifetimes

Measurements of $b$-hadron lifetimes are reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0fb$^{-1}$, collected by the LHCb detector at a centre-of-mass energy of $7$Tev. Using the exclusive decays $B^+\to J/\psi K^+$, $B^0\to J/\psi K^*(892)^0$, $B^0\to J/\psi K^0_{\rm S}$, $\Lambda_b^0\to J/\psi \Lambda$ and $B^0_s\to J/\psi \phi$ the average decay times in these modes are measured to be $\tau_{B^+\to J/\psi K^+}$ = $1.637 \pm$ 0.004 $\pm$ 0.003 ps, $\tau_{B^0\to J/\psi K^*(892)^0}$ = $1.524 \pm$ 0.006 $\pm$ 0.004 ps, $\tau_{B^0\to J/\psi K^0_{\rm S}}$ = $1.499 \pm$ 0.013 $\pm$ 0.005 ps, $\tau_{\Lambda_b^0\to J/\psi \Lambda}$ = $1.415 \pm$ 0.027 $\pm$ 0.006 ps and $\tau_{B^0_s\to J/\psi \phi}$ = $1.480 \pm$ 0.011 $\pm$ 0.005 ps, where the first uncertainty is statistical and the second is systematic. These represent the most precise lifetime measurements in these decay modes. In addition, ratios of these lifetimes, and the ratio of the decay-width difference, $\Delta\Gamma_d$, to the average width, $\Gamma_d$, in the $B^0$ system, $\Delta \Gamma_d/\Gamma_d = -0.044 \pm 0.025 \pm 0.011$, are reported. All quantities are found to be consistent with Standard Model expectations.

Design and evaluation of a device for fast multispectral time-resolved fluorescence spectroscopy and imaging

The application of time-resolved fluorescence spectroscopy (TRFS) to in vivo tissue diagnosis requires a method for fast acquisition of fluorescence decay profiles in multiple spectral bands. This study focusses on development of a clinically compatible fiber-optic based multispectral TRFS (ms-TRFS) system together with validation of its accuracy and precision for fluorescence lifetime measurements. It also presents the expansion of this technique into an imaging spectroscopy method. A tandem array of dichroic beamsplitters and filters was used to record TRFS decay profiles at four distinct spectral bands where biological tissue typically presents fluorescence emission maxima, namely, 390, 452, 542, and 629 nm. Each emission channel was temporally separated by using transmission delays through 200 μm diameter multimode optical fibers of 1, 10, 19, and 28 m lengths. A Laguerre-expansion deconvolution algorithm was used to compensate for modal dispersion inherent to large diameter optical fibers and the finite bandwidth of detectors and digitizers. The system was found to be highly efficient and fast requiring a few nano-Joule of laser pulse energy and <1 ms per point measurement, respectively, for the detection of tissue autofluorescent components. Organic and biological chromophores with lifetimes that spanned a 0.8-7 ns range were used for system validation, and the measured lifetimes from the organic fluorophores deviated by less than 10% from values reported in the literature. Multi-spectral lifetime images of organic dye solutions contained in glass capillary tubes were recorded by raster scanning the single fiber probe in a 2D plane to validate the system as an imaging tool. The lifetime measurement variability was measured indicating that the system provides reproducible results with a standard deviation smaller than 50 ps. The ms-TRFS is a compact apparatus that makes possible the fast, accurate, and precise multispectral time-resolved fluorescence lifetime measurements of low quantum efficiency sub-nanosecond fluorophores.

Mass and lifetime measurements at the experimental storage ring of GSI

Precision mass and β-lifetime measurements conducted at the experimental storage ring ESR in Darmstadt are reviewed. Relativistic radioactive isotopes can be produced by projectile fragmentation and fission reactions, separated in flight by the fragment separator FRS, and injected into the cooler-storage ring ESR. This powerful experimental method gives access to all fragments with half-lives down to the sub-millisecond range. The research potential is demonstrated by several examples of precision mass and lifetime measurements. A particular emphasis is given to the worldwide unique experimental program at the ESR on the studies of bound-state β− decay.

Precision lifetime measurements of the first 2+and 4+states in56Cr at theN=32subshell closure

Precision lifetime measurements of the first 2<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mo>+</mml:mo></mml:msup></mml:math>and 4<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mo>+</mml:mo></mml:msup></mml:math>states in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mrow /><mml:mn>56</mml:mn></mml:msup></mml:math>Cr at the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>N</mml:mi><mml:mo>=</mml:mo><mml:mn>32</mml:mn></mml:mrow></mml:math>subshell closure

Status report on the setup for the decay rate measurement of the negative positronium ion

The negative positronium ion Ps− is a bound system consisting of two electrons and a positron. Its three constituents are point-like and stable leptonic particles with equivalent mass, which are only subjected to the electroweak and the gravitational force. Hence Ps− represents an ideal object to study the quantum mechanics of three-body systems.We present a status report on a new a measurement setup, which was used to perform several high precision lifetime measurements at the NEPOMUC facility. The combined results of systematic test measurements are discussed and an outlook to future measurements as well as preliminary results of the most recent beam time will be given.

Minority carrier lifetime imaging of silicon wafers calibrated by quasi-steady-state photoluminescence

Reliable process control or predictions of solar cell efficiencies from minority carrier lifetimes on silicon wafers require precise lifetime measurements. For inhomogeneous material quality this implies the necessity of adequately averaged spatially resolved lifetime measurements. Materials such as, e.g. multicrystalline upgraded metallurgical grade silicon frequently feature relatively low lifetimes, high trap densities, and several material parameters (charge carrier mobilities and net dopant concentration) that are not straightforwardly predictable or measurable. As this may substantially compromise conventional lifetime measurements, we present a solely luminescence based lifetime imaging technique, which requires virtually no a priori information about material parameters. Our approach is based on a calibration of a wafer's photoluminescence image through a precise lifetime determination of a part of this wafer via quasi-steady-state photoluminescence. Carrier mobilities, net dopant concentration, and surface morphology leave the determination of lifetime virtually unaffected, the injection dependence of lifetime is properly taken into account, and lifetimes down to the timescale of a microsecond can be reliably measured.

Fluorescence lifetime endoscopy using TCSPC for the measurement of FRET in live cells.

Development of remote imaging for diagnostic purposes has progressed dramatically since endoscopy began in the 1960’s. The recent advent of a clinically licensed intensity-based fluorescence micro-endoscopic instrument has offered the prospect of real-time cellular resolution imaging. However, interrogating protein-protein interactions deep inside living tissue requires precise fluorescence lifetime measurements to derive the Förster resonance energy transfer between two tagged fluorescent markers. We developed a new instrument combining remote fiber endoscopic cellular-resolution imaging with TCSPC-FLIM technology to interrogate and discriminate mixed fluorochrome labeled beads and expressible GFP/TagRFP tags within live cells. Endoscopic-FLIM (e-FLIM) data was validated by comparison with data acquired via conventional FLIM and e-FLIM was found to be accurate for both bright bead and dim live cell samples. The fiber based micro-endoscope allowed remote imaging of 4 µm and 10 µm beads within a thick Matrigel matrix with confident fluorophore discrimination using lifetime information. More importantly, this new technique enabled us to reliably measure protein-protein interactions in live cells embedded in a 3D matrix, as demonstrated by the dimerization of the fluorescent protein-tagged membrane receptor CXCR4. This cell-based application successfully demonstrated the suitability and great potential of this new technique for in vivo pre-clinical biomedical and possibly human clinical applications.

γ-ray spectroscopy study of states inSi27relevant for theAl26m(p,γ)Si27reaction in novae and supernovae

The heavy-ion, fusion-evaporation reaction C12(O16,n) was used to identify γ-decay transitions from excited states in Si27 above the proton threshold. The precise level energy measurements, Jπ assignments, and lifetime measurements of astrophysically important Al26m+p resonances have allowed an evaluation of the Al26m(p,γ)Si27 reaction rate. An lp=0 resonance has been newly identified at a center-of-mass energy in the Al26m+p system of 146.3(3) keV and is expected to dominate the rate for low stellar temperatures. In addition, an lp=1 resonance has been identified at 378.3(30) keV and is likely to dominate the rate at high astrophysical temperatures, such as those found in oxygen-neon novae and core-collapse supernovae. © 2009 The American Physical Society.

Problems with accurate atomic lifetime measurements of multiply charged ions

A number of recent atomic lifetime measurements on multiply charged ions have reported uncertainties lower than 1%. Such a level of accuracy challenges theory, which is a good thing. However, a few lessons learned from earlier precision lifetime measurements on atoms and singly charged ions suggest that one should remain cautious about the systematic errors of experimental techniques.

Spectroscopy with trapped highly charged ions

We give an overview of atomic spectroscopy performed on electron beam ion traps at various locations throughout the world. Spectroscopy at these facilities contributes to various areas of science and engineering, including but not limited to basic atomic physics, astrophysics, extreme ultraviolet lithography, and the development of density and temperature diagnostics of fusion plasmas. These contributions are accomplished by generating, for example, spectral surveys, making precise radiative lifetime measurements, accounting for radiative power emitted in a given wavelength band, illucidating isotopic effects, and testing collisional–radiative models. While spectroscopy with electron beam ion traps had originally focused on the x-ray emission from highly charged ions interacting with the electron beam, the operating modes of such devices have expanded to study radiation in almost all wavelength bands from the visible to the hard x-ray region; and at several facilities the ions can be studied even in the absence of an electron beam. Photon emission after charge exchange or laser excitation has been observed; and the work is no longer restricted to highly charged ions. Much of the experimental capabilities are unique to electron beam ion traps, and the work performed with these devices cannot be undertaken elsewhere. However, in other areas the work on electron beam ion traps rivals the spectroscopy performed with conventional ion traps or heavy-ion storage rings. The examples we present highlight many of the capabilities of the existing electron beam ion traps and their contributions to physics.