Improved signal processing in pulsed and cw spin-flip Raman laser spectrometers

Double beam optical techniques which allow direct spectroscopic measurements using both pulsed and cw tunable spin-flip Raman lasers have been developed. The systems provide a high resolution spectrometer (spectral linewidths 0.03 cm^-1 pulsed and 0.003 cm^-1 cw) in the range 5.3–6μm. Line frequency measurements are accurate to 0.01 cm^-1 and intensity measurements to a few percent. Results of molecular spectroscopy provide a comparison of the relative performance of each system.     

High-resolution spectroscopy on trapped molecular ions in rotating electric fields: A new approach for measuring the electron electric dipole moment

High-resolution molecular spectroscopy is a sensitive probe for violations of fundamental symmetries. Symmetry violation searches often require, or are enhanced by, the application of an electric field to the system under investigation. This typically precludes the study of molecular ions due to their inherent acceleration under these conditions. Circumventing this problem would be of great benefit to the high-resolution molecular spectroscopy community since ions allow for simple trapping and long interrogation times, two desirable qualities for precision measurements. Our proposed solution is to apply an electric field that rotates at radio frequencies. We discuss considerations for experimental design as well as challenges in performing precision spectroscopic measurements in rapidly time-varying electric fields. Ongoing molecular spectroscopy work that could benefit from our approach is summarized. In particular, we detail how spectroscopy on a trapped diatomic molecular ion with a ground or metastable ³Δ₁ level could prove to be a sensitive probe for a permanent electron electric dipole moment (eEDM).     

The TITAN mass measurement facility at TRIUMF-ISAC

The TITAN facility at TRIUMF-ISAC will use four ion traps with the primary goal of determining nuclear masses with high precision, particularly for short lived isotopes with lifetimes down to approximately 10 ms. The design value for the accuracy of the mass measurement is 1 ×10^???8. The four main components in the facility are an RF cooler/buncher (RFCT) receiving the incoming ion beam, an electron beam ion trap (EBIT) to breed the ions to higher charge states, a cooler Penning trap (CPET) to cool the highly charged ions, and finally the measurement Penning trap (MPET) for the precision mass determination. Additional goals for this system are laser spectroscopy on ions extracted from the RFCT and beta spectroscopy in the EBIT (in Penning trap mode) on ions that are purified using selective buffer gas cooling in the CPET. The physics motivation for the mass measurements are manifold, from unitarity tests of the CKM matrix to nuclear structure very far from the valley of stability, nuclear astrophysics and the study of halo-nuclei. As a first measurement the mass of ¹¹Li will be determined. With a lifetime of 8.7 ms and a demonstrated production rate of 4×10⁴ ions/sec at ISAC the goal for this measurement at TITAN is a relative uncertainty of 5×10^???8. This would check previous conflicting measurements and provide information for nuclear theory and models.     

On-line nuclear orientation study of184Au

The¹⁸⁴Au→¹⁸⁴Pt decay, studied on-line with the UNISOR facility at HHIRF, is discussed. Gamma-ray and conversion-electron spectroscopy of¹⁸⁴Pt as well as on-line nuclear orientation measurements of¹⁸⁴Au were done. A new low-lying level scheme of¹⁸⁴Pt is proposed. Two coexisting bands with different deformations and their respective γ-vibrational bands are established. Internal conversion coefficients for interband transitions between states with the same spin are extracted from the spectroscopy measurements. The relative E0 contents of the transitions are determined by combining internal conversion coefficients with E2/M1 mixing ratios deduced from gamma-ray anisotropies measured from oriented nuclei.     

Electric quadrupole interactions of europium in alkali europium tungstates by Mössbauer and laser spectroscopies

¹⁵¹Eu Mössbauer spectroscopy and optical-r.f. double resonance spectroscopy measurements of the quadrupole interaction parameters in KEu(WO₄)₂ give good agreement and are of comparable accuracy, while laser heterodyne spectroscopy measurements provided improved accuracy by an order of magnitude. However in the crystallographically disordered compound NaEu(WO₄)₂, Mössbauer spectroscopy was more suited to producing fittable spectra. The difference in the hyperfine field of the two compounds in a 9 T applied field is attributed to a transferred hyperfine interaction.     

238U and 57Fe Mössbauer Spectroscopic Study of UFe2

We have performed ⁵⁷Fe and ²³⁸U Mössbauer measurements of UFe₂ in order to investigate its magnetic properties. From the results of ⁵⁷Fe Mössbauer spectroscopy, the ferrromagnetic ordering at 167 K is caused by the iron 3d-electrons, which hybridize strongly with the uranium 5f-conduction electrons. It is also clarified from the results of ²³⁸U Mössbauer spectroscopy that there are no magnetic moments on the uranium atoms.     

Production and investigations of negative osmium ions for fundamental applications: REOSTRAP

High quality measurements in respect to accuracy, resolving power and sensitivity using negative osmium ions confined in ion traps will contribute to answer questions in modern fundamental physics. A proposed system to carry out these measurements would require a laser desorption ion source, and an ion-trap system. Following the recent laser spectroscopy investigations at the Max-Planck Institute for Nuclear Physics in Heidelberg, the goals of the proposed system should focuss on the laser cooling of negative osmium ions since such a system could be used to cool antiprotons to very low temperatures via collisions (sympathetic cooling) for efficient antihydrogen formation in its ground state. Furthermore, together with rhenium ions, the confinement of osmium ions in a Penning trap is important to determine the mass difference ¹⁸⁷Re-¹⁸⁷Os, and therefore the Q-value in the decay of ¹⁸⁷Re (T _1/2?=?4×10¹⁰ years) with unprecedented accuracy. This Q-value is an important constraint for the determination of the mass of the electron antineutrino as aimed by the international MARE collaboration. In this paper several mechanisms are considered for the preparation of the negative ions in order to apply laser cooling.     

Physical investigation of the mechanisms of lithium insertion in sulfides as anode materials for lithium-ion batteries

Electrochemical and chemical lithium insertion (vian-butyllithium) were carried out on a family of spinel phases of the Cu₂S-In₂S₃-SnS₂ system. Electrochemical measurements have revealed great reversible capacities and the possible use of these materials as negative electrodes in lithium-ion batteries.¹¹⁹Sn Mössbauer spectroscopy,⁷Li NMR and S K edge EXAFS spectroscopy were carried out to characterize the mechanisms of lithium insertion. This study has shown the formation of lithium-metal alloys finely dispersed in an amorphous lithium sulfide matrix at low potentials. A model is proposed to explain the great capacities observed in these materials.     

Towards higher sensitivity and lighter elements by collinear laser spectroscopy at isolde

New resonance detection mechanisms based on atom or ion counting instead of fluorescence photon detection have been introduced in collinear laser spectroscopy at ISOLDE. This increased the sensitivity by several orders of magnitude and allowed measurements on short-lived isotopes very far from stability, which are available in minor quantities only (≤10³ ions per second). Results of recent measurements on the medium mass and light elements Sr, Kr, Ca and Li are presented.     

Precision two-photon spectroscopy of alkali elements

In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6s ² S _1/2 level of ³⁹K and ⁴¹K, 9s ² S _1/2level and 7d ² D _3/2 level of ¹³³Cs are also discussed.     

Magnetic susceptibility and 119Sn Mössbauer spectroscopy studies of RAuSn compounds (R=La, Ce, Pr)

In this paper the results of bulk magnetic susceptibility measurements and ¹¹⁹Sn Mössbauer spectroscopy measurements of LaAuSn, CeAuSn and PrAuSn intermetallic compounds are presented. New phase transitions in CeAuSn and PrAuSn compounds have been found by both methods employed. Structural and electronic properties are discussed.     

Temperature and water concentration measurements in combustion gases using a DFB diode laser at 1.4 μm

A sensor using a single DFB diode laser at 1.4 μm based on wavelength modulation spectroscopy for the measurements of the gas temperature and the H₂O concentration in combustion gases is developed. A line pair of H₂O absorption transitions located at 7085.251 and 7085.876 cm^?1 is selected based on some design rules. The 1f normalized 2f method is used to remove the need for the calibration and to correct for the transmission variation due to beam steering, mechanical misalignments, soot, and window fouling. The precision for the temperature and H₂O concentration measurements are 1.05 and 2.10% in a controlled static cell, respectively. Burner experiments demonstrate the ability of the system for in situ measurements.     

An Ensemble and Single-molecule Fluorescence Spectroscopy Investigation of Calcium Green 1, a Calcium-ion Sensor

The calcium-ion indicator dye, Calcium Green 1 (CG-1), has been characterized using a combination of ensemble and single-molecule optical spectroscopy measurements. In terms of ensemble measurements, CG-1 demonstrated a strong increase in fluorescence emission as a function of increasing [Ca²⁺]. This was accompanied by a change in the relative proportions of two chemical forms of the dye, each with a different fluorescence lifetime, which were found to co-exist in solution. From single-molecule fluorescence measurements, it was found that the fluorescence intensity and photobleaching time (on-time) of each CG-1 molecule was invariant with [Ca²⁺] and that changes in ensemble fluorescence intensity simply correlates with the number of fluorescent molecules in solution. These results are compared with that of the related system, Calcium Green 2 (CG-2), and the mechanisms of operation of these two indicator dyes are discussed.     

New measurements and global analysis of rotational spectra of Cl-, Br-, and I-benzene: Spectroscopic constants and electric dipole moments

The data available from rotational spectroscopy for chlorobenzene, bromobenzene, and iodobenzene have been extended by new measurements in the mm-wave region and in supersonic expansion in the cm-wave region. All available ground state measurements have been combined in global fits to derive precise rotational, centrifugal, and nuclear quadrupole coupling constants for the molecules. Rotational transitions in first excited states of the lowest frequency normal modes in bromobenzene and iodobenzene have been assigned and fitted. The values of electric dipole moments for ³⁵Cl-, ⁷⁹Br-, ⁸¹Br-, and I-benzene have been determined from Stark effect measurements on selected hyperfine components in the supersonic expansion spectrum, and are compared with values for several other series of monohalogen molecules.     

X‐Treme beamline at SLS: X‐ray magnetic circular and linear dichroism at high field and low temperature

X‐Treme is a soft X‐ray beamline recently built in the Swiss Light Source at the Paul Scherrer Institut in collaboration with École Polytechnique Fédérale de Lausanne. The beamline is dedicated to polarization‐dependent X‐ray absorption spectroscopy at high magnetic fields and low temperature. The source is an elliptically polarizing undulator. The end‐station has a superconducting 7 T–2 T vector magnet, with sample temperature down to 2 K and is equipped with an in situ sample preparation system for surface science. The beamline commissioning measurements, which show a resolving power of 8000 and a maximum flux at the sample of 4.7 × 10¹² photons s^?1, are presented. Scientific examples showing X‐ray magnetic circular and X‐ray magnetic linear dichroism measurements are also presented.     

Laser spectroscopy of stable Os isotopes

Doppler-free isotope shift measurements of the stable even ^184–192Os and ^187,189Os odd isotopes have been performed for the first time on the 5d ⁶6s ^{2 5}D₄→5d ⁶6s6p ⁷F₄ (305.9 nm) transition in the neutral atom by atomic beam laser spectroscopy and on the ionic 5d ⁶6s ⁵D_9/2→5d ⁶6p ⁶D_7/2 (228.2 nm) transition by fast collinear ion-laser spectroscopy. The measurements were carried out in Manchester and at the IGISOL facility in Jyväskylä in Finland, respectively. The results presented are the most precise measurements to-date of the absolute isotope shifts.     

Measurements of the atmospheric concentrations of nitrogen dioxide using the radiation absorption in a spectral range of 415 nm

The trace atmospheric concentrations of NO₂ are measured with the methods of the diode laser absorption spectroscopy and the phase shift of the modulated radiation. An electronic transition in a range of 415 nm is employed. For a measurement time of 20 ms, the sensitivity of the concentration measurements is about 10^?11 relative to the concentration of air particles (0.02 ppbv). At a time interval of 5–10 min, the reproducibility of the absolute concentration measurements (0.1 ppbv) is limited by the low-frequency fluctuations of the optical parameters of the spectrometer and the calibration system and corresponds to the level determined by the Allan variance.     

Status of an R&D project of a positron gun at “Horia Hulubei” NIPNE Bucharest

A new positron gun (PG) will enable high sensitivity measurements in applications of positron annihilation spectroscopy in Romania. Some data concerning the design of a modular system for focussing, transport and acceleration of mono-energetic positrons in the range 0.8-50 keV have been obtained and experimenting on moderators and CDBS was performed. We present a short overview of the present status of the project and preliminary results from Coincidence Doppler Broadening Spectroscopy with a ²²NaCl source, on Al samples. The entire positron gun system will be designed as a high-vacuum dedicated extension operating with two options: a 50 mCi ²²NaCl source and in-line with the NIPNE cyclotron or a new intense compact cyclotron.     

Overview of the current spectroscopy effort on the Livermore electron beam ion traps

An overview is given of the current spectroscopic effort on the Livermore electron beam ion trap facilities. The effort focuses on four aspects: spectral line position, line intensity, temporal evolution, and line shape. Examples of line position measurements include studies of the K-shell transitions in heliumlike Kr³⁴⁺ and the 2s-2p intrashell transitions in lithiumlike Th⁸⁷⁺ and U⁸⁹⁺, which provide benchmark values for testing the theory of relativistic and quantum electrodynamical contributions in high-Z ions. Examples of line intensity measurements are provided by measurements of the electron-impact excitation and dielectronic recombination cross sections of the heliumlike transition-metal ions Ti²⁰⁺ through Co²⁵⁺. A discussion of radiative lifetime measurements of metastable levels in heliumlike ions is given to illustrate our time-resolved spectroscopy techniques in the microsecond range. We also present a measurement of the spectral lineshape that illustrates the very low ion temperatures that can be achieved in an EBIT.     

Field measurements of volcanic gases using tunable diode laser based mid-infrared and Fourier transform infrared spectrometers

The first field measurements of volcanic gases using mid-IR difference frequency laser spectroscopy are reported. The results were obtained at the summit crater of Masaya volcano, Nicaragua, with the gases being drawn into a multi-pass cell and measured at reduced pressure. Automated sensitive and selective detection of CO₂, SO₂, H^35,37Cl, H₂O, and CH₄ was achieved. Simultaneous measurements obtained with open-path Fourier transform spectroscopy provide a useful comparison of the two optical techniques. We also consider the potential measurement of CO₂ isotopic ratios in volcanic gases using laser-based spectroscopy.