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I describe recent advances made in Doppler spectroscopy of low mass star and discuss how they perform on public observations ontained with the HARPS spectrograph. This work is possible thanks to the recent development of the HARPS-TERRA software (Template Enhanced Radial velocity Re-analysis Application), which obtains precision RV measurements by least-squares matching each spectrum to a high SNR template built from the same observations. As a result, we obtain a substantial increase in precision compared to the traditional cross-correlation methods. The increase in precision is demonstrated with RV measurements on stable M dwarfs (80 cm/s over time-scales of years) and the early detection of several very low mass candidates. Moreover, the ability of HARPS-TERRA in reproducing the observed spectra at high fidelity allows us to explore new effects including : wavelength dependence of activity induced Doppler signals, simultaneous measurement of orbital obliquities and stellar rotation profiles and, when combined with advanced Bayesian data analysis techniques, small Doppler signals likely caused by new super-Earth mass candidates in the habitable zones of nearby stars.

We present a set of new synthetic diagnostics, recently implemented in the ERO code, that were developed to facilitate direct comparisons between experiments and modelling of tokamak scrape–off–layer plasmas. The diagnostics calculate the spectroscopic Doppler shift and Doppler broadening of impurity lines of interest for any line of sight, as well as generate camera images from arbitrary viewing angles allowing for curvilinear (e.g. wide angle or fisheye) lenses. The synthetic camera diagnostics can either replicate the distortions caused by curvilinear lenses, or alternatively, create a rectilinear synthetic camera image and correct the curvilinear distortions in the experimental image. Comparison to experimental data is presented.

A variation on velocity-aligned Doppler spectroscopy is used to probe the nuclear hyperfine states of atomic hydrogen resulting from the 193 nm photodissociation of HBr. By utilizing 1 + 1 resonance-enhanced ionization through the Lyman-α transition along with a novel experimental approach, one can observe the onset of Stark effects that come about because of the modest electric field present in the ionization region of the mass spectrometer. A straightforward theoretical treatment is used to address the observed behavior.

The photodissociation dynamics of HOBr to give OH + Br fragments is investigated at 490 and 510 nm, close to the threshold for dissociation. The available energy resulting from dissociation at these wavelengths corresponds respectively to ∼3500 and ∼2700 cm-1. The nascent OH photofragments are characterized via polarization and Doppler spectroscopy using laser-induced fluorescence. At both wavelengths the OH fragments are found to be in their vibrational ground state with approximately ∼150 cm-1 of rotational excitation. Almost the entire allotment of available energy is deposited into relative translation of the products (∼95%). An analysis of the OH Doppler line shapes reveals that the 〈μ·v〉 correlation parameter is strongly positive (βμv = 0.72), indicating a definite preference for parallel alignment of the electronic transition moment and the recoil velocity vector of HOBr. This trend is independent of the photolysis wavelengths examined within the visible absorption band. All other vector correlati...

Ferroelectric Pb(Zr60Ti40)O-3 ceramics sintered for 6 hours at 1050 degreesC in air and doped with La or Nb in the range 0.5 to 6 mol% have been investigated by positron lifetime spectroscopy and two-dimensional coincident Doppler measurements. The undoped samples show two lifetime components with a defect lifetime of about 250 ps. After doping this defect lifetime increases to about 295 ps. The influence of the doping on the Doppler spectra is extremely small. Additional XRD pattern show a significant correlation between doping and lattice structure.

We have employed the Cologne terahertz spectrometer [ 1,2] to observe Lamb dip and crossover phenomena in rotational spectra at 572 GHz. Because of the large power output of the backward wave oscillators used in the system, no special means are required to induce this saturation effect; the coincidentally reflected radiation from the bolometer present in our quasi-optical absorption cell is sufficient to saturate the υz = 0 sub-group. This effect has allowed the observation of the three previously unresolved hyperfine components of the l4NH3 A ← S, JK = 10 ← 00 transition, and was also observed for the analogous 15NH3 transition in natural abundance (i. e. 0.366 %). These measurements indicate a possible improvement of molecular transition frequencies in the submillimeter region.

A variation of velocity‐aligned Doppler spectroscopy is used to study F=0 and F=1 nuclear hyperfine populations in the ground electronic state of atomic hydrogen as the result of a chemical reaction. In this case, the reaction is the 193 nm photolysis of HBr. Not only can the nuclear hyperfine states be studied, but the method allows unequivocal correlation with the spin–orbit states of the bromine atom, i.e., Br(2P1/2) and Br(2P3/2). For H atoms correlated with Br(2P3/2), the F=0/F=1 is 1.2±0.2. Future directions involving the study of this fundamental chemical product state distribution are also discussed.

Sub-Doppler spectroscopy of molecular cesium X-A transition near 1083 nm has been performed using InGaAs distributed Bragg reflector semiconductor lasers. The sub-Doppler recordings of the 4 He triplet lines were used as reference wavelengths, and the absolute wavelengths of several Cs 2 lines were determined with an accuracy of 1 part in 10 8 . An improvement in the frequency stability was demonstrated by locking one laser to a Cs 2 transition and the second laser to a 4 He transition.

Temperature anisotropy in broad component of H$\alpha$ line was found in the ring trap 1 (RT-1) device by Doppler spectroscopy. Since hot hydrogen neutrals emitting a broad component are mainly produced by charge exchange between neutrals and protons, the anisotropy in the broad component is the evidence of proton temperature anisotropy generated by betatron acceleration.

The 'holy grail' of exoplanet research today is the detection of an earth-like planet: a rocky planet in the habitable zone around a main-sequence star. Extremely precise Doppler spectroscopy is an indispensable tool to find and characterize earth-like planets; however, to find these planets around solar-type stars, we need nearly one order of magnitude better radial velocity (RV) precision than the best current spectrographs provide. Recent developments in astrophotonics (Bland-Hawthorn & Horton 2006, Bland-Hawthorn et al. 2010) and adaptive optics (AO) enable single mode fiber (SMF) fed, high resolution spectrographs, which can realize the next step in precision. SMF feeds have intrinsic advantages over multimode fiber or slit coupled spectrographs: The intensity distribution at the fiber exit is extremely stable, and as a result the line spread function of a well-designed spectrograph is fully decoupled from input coupling conditions, like guiding or seeing variations (Ihle et al. 2010). Modal noise, a limiting factor in current multimode fiber fed instruments (Baudrand & Walker 2001), can be eliminated by proper design, and the diffraction limited input to the spectrograph allows for very compact instrument designs, which provide excellent optomechanical stability. A SMF is the ideal interface for new, very precise wavelength calibrators, like laser frequency combs (Steinmetz et al. 2008, Osterman et al. 2012), or SMF based Fabry-Perot Etalons (Halverson et al. 2012). At near infrared wavelengths, these technologies are ready to be implemented in on-sky instruments, or already in use. We discuss a novel concept for such a spectrograph., IAU Proceedings, General Assembly 2012. 4 pages

We present initial results from a new high-contrast imaging program dedicated to stars that exhibit long-term Doppler radial velocity accelerations (or "trends"). The goal of the TRENDS (TaRgetting bENchmark-objects with Doppler Spectroscopy and) imaging survey is to directly detect and study the companions responsible for accelerating their host star. In this first paper of the series, we report the discovery of low-mass stellar companions orbiting HD 53665, HD 68017, and HD 71881 using NIRC2 adaptive optics (AO) observations at Keck. Follow-up imaging demonstrates association through common proper-motion. These co-moving companions have red colors with estimated spectral-types of K7--M0, M5, and M3--M4 respectively. We determine a firm lower-limit to their mass from Doppler and astrometric measurements. In the near future, it will be possible to construct three-dimensional orbits and calculate the dynamical mass of HD 68017 B and possibly HD 71881 B. We already detect astrometric orbital motion of HD 68017 B, which has a projected separation of 13.0 AU. Each companion is amenable to AO-assisted direct spectroscopy. Further, each companion orbits a solar-type star, making it possible to infer metallicity and age from the primary. Such benchmark objects are essential for testing theoretical models of cool dwarf atmospheres., Accepted to ApJ, comments welcome

Accurate molecular spectroscopy in the mid-infrared region allows precision measurements of fundamental constants. For instance, measuring the linewidth of an isolated Doppler-broadened absorption line of ammonia around 10 $\mu$m enables a determination of the Boltzmann constant k B. We report on our latest measurements. By fitting this lineshape to several models which include Dicke narrowing or speed-dependent collisional effects, we find that a determination of k B with an uncertainty of a few ppm is reachable. This is comparable to the best current uncertainty obtained using acoustic methods and would make a significant contribution to any new value of k B determined by the CODATA. Furthermore, having multiple independent measurements at these accuracies opens the possibility of defining the kelvin by fixing k B, an exciting prospect considering the upcoming redefinition of the International System of Units., Comment: proceedings of the ICAP 2012 conference (23rd International Conference on Atomic Physics). arXiv admin note: text overlap with arXiv:1309.4549

Doppler spectroscopy has uncovered or confirmed all the known planets orbiting nearby stars. Two main techniques are used to obtain precision Doppler measurements at optical wavelengths. The first approach is the gas cell method, which consists on the least-squares matching of the spectrum of Iodine imprinted on the spectrum of the star. The second method relies on the construction of a stabilized spectrograph externally calibrated in wavelength. The most precise stabilized spectrometer in operation is HARPS, operated by ESO in La Silla Observatory/Chile. The Doppler measurements obtained with HARPS are typically obtained using the Cross-Correlation Function technique (CCF). It consists of multiplying the stellar spectrum with a weighted binary mask and finding the minimum of such product as a function of the Doppler shift. It is known that CCF is suboptimal in exploiting the Doppler information in the stellar spectrum. Here, we describe an algorithm to obtain precision RV measurements using least-squares matching of each observed spectrum to a high signal-to-noise ratio template derived from the same observations. Such algorithm is implemented in our software called HARPS-TERRA (Template Enhanced Radial velocity Re-analysis Application). New radial velocity measurements on a representative sample of stars observed by HARPS is used to illustrate the benefits of the proposed method. We show that, compared to CCF, template matching provides a significant improvement in accuracy, specially when applied to M dwarfs., Comment: Accepted in ApJ supplement series. Main manuscript contains 40 pages, 17 figures and 6 Tables. Table 7 to 14 (page 41-90) contain the relevant time series. Table 15 contains the HARPS-TERRA, HIRES and PFS RV measurements used in http://arxiv.org/abs/1202.0446. Machine readable tables will the provided in the journal version of the manuscript

The a 3P0-y 3D10 Ti I transition at 592.2 nm was investigated by using a hollow-cathode discharge. Sub-Doppler resolution was obtained by combining optogalvanic detection with saturation spectroscopy and the non-linear Hanle effect. The upper state Lande factor was also determined by Zeeman intermodulated spectroscopy.

A method is developed for extracting the photofragment speed distribution function from a velocity aligned Doppler spectrum. This method is used to determine the distribution function of HCl produced by 193 nm photodissociation of vinyl chloride. The speed distribution of the Cl fragment is determined by the method of magic angle Doppler spectroscopy.

The collision dynamics of the OH + Ar/He systems have been studied following production of the translationally and rotationally aligned radical species via polarized photolysis of H 2 O 2 at a wavelength of 248 nm. Elastically scattered OH molecules were probed via polarized Fourier-transform Doppler spectroscopy. The manner in which the speed distribution and laboratory speed averaged translational anisotropy of the OH photofragments change with time is well reproduced by a hard sphere collision model. In addition, the degradation of the laboratory speed averaged v-j correlation by collision with argon is best reproduced if the direction of the OH rotational angular momentum vector is conserved throughout an elastic collision encounter.

Final state resolved vector properties of the reaction H (2S)+O2(3Σ−g)→OH(2Π)+O(3P) have been measured using Doppler spectroscopy. Velocity‐aligned H atoms were generated by photodissociation of H2S with linearly polarized ArF excimer laser light. The correlated velocity and angular momentum distribution of nascent OH reaction products was probed by laser induced fluorescence. Techniques are described for analyzing the line shapes, modeling the bipolar moments of the OH velocity and angular momentum distribution as parametric functions of the scattering angle. Distinctive Doppler‐broadened lineshapes indicate scattering angle distributions with a strong forward and a weaker backward maximum. A qualitatively different angular momentum polarization for the two lambda doublet components of the OH product is required to explain the Doppler profiles.

On the basis of density matrix equations, we theoretically investigated narrow sub-Doppler resonances in the spectral distribution of a number of atomic particles (atoms or molecules) optically excited in a metastable state in an ultrathin gas cell with the inner thickness less than or of the order of the wavelength λ ≤ 1 μm of the monochromatic light wave incident in the normal direction. Essential dependence of these resonances (on the center of the optical transition) was analyzed versus the inner thickness and transversal size of such a gas cell and also versus the intensity of the incident wave. Investigated resonances may be applied as references in high-accuracy optical frequency standards and for high precision measurements.

A summary is given of the work carried out under the LDRD project 09-ERD-025 entitled Scrape-Off-Layer Flow Studies in Tokamaks. This project has lead to implementation of the new prototype Fourier Transform Spectrometer edge plasma flow diagnostic on the DIII-D National Fusion Facility at General Atomics, acquisition of carbon impurity concentration and flow data, and demonstration that the resulting data compare reasonably well with LLNL's edge plasma transport code UEDGE. Details of the work are contained in attached published papers, while the most recent results that are being written-up for publication are summarized in the report. Boundary plasma flows in tokamak fusion devices are key in determining the distribution of fuel and impurity ions, with tritium build-up in the walls an especially critical operational issue. The intrusion of impurity ions to the hot plasma core region can result in serious energy-loss owing to line radiation. However, flow diagnostic capability has been severely limited in fusion-relevant hot edge plasmas where Langmuir-type probes cannot withstand the high heat flux and traditional Doppler spectroscopy has limited resolution and signal strength. Thus, new edge plasma flow diagnostic capabilities need to be developed that can be used in existing and future devices such as ITER. The understanding of such flows requires simulation with 2-dimensional transport codes owing to the geometrical complexity of the edge region in contact with material surfaces and the large number of interaction physical processes including plasma flow along and across the magnetic field, and coupling between impurity and neutral species. The characteristics of edge plasma flows are substantially affected by cross-magnetic-field drifts (ExB/B{sup 2} and BxVB/B{sup 2}), which are known to introduce substantial convergence difficulty for some cases. It is important that these difficulties be overcome so that drifts can be included in transport models, both for validation with existing data and for projection to future devices.

The H- and D-atom products from collisional quenching of OD A (2)Σ(+) by H(2) are characterized through Doppler spectroscopy using two-photon (2 (2)S ←← 1 (2)S) laser-induced fluorescence. Partial deuteration enables separation of the channel forming H + HOD products, which accounts for 75% of reactive quenching events, from the D + H(2)O product channel. The Doppler profiles, along with those reported previously for other isotopic variants, are transformed into product translational energy distributions using a robust fitting procedure based on discrete velocity basis functions. The product translational energy distribution for the H-atom channel is strongly peaked at low energy (below 0.5 eV) with a long tail extending to the energetic limit. By contrast, the D-atom channel exhibits a small peak at low translational energy with a distinctive secondary peak at higher translational energy (approximately 1.8 eV) before falling off to higher energy. In both cases, most of the available energy flows into internal excitation of the water products. Similar distributions are obtained upon reanalysis of D- and H-atom Doppler profiles, respectively, from reactive quenching of OH A (2)Σ(+) by D(2). The sum of the translational energy distributions for H- and D-atom channels is remarkably similar to that obtained for OH A (2)Σ(+) + H(2), where the two channels cannot be distinguished from one another. The product translational energy distributions from reactive quenching are compared with those obtained from a previous experiment performed at higher collision energy, quasiclassical trajectory calculations of the post-quenching dynamics, and a statistical model.

In this paper, we present significant progress performed on an experiment dedicated to the determination of the Boltzmann constant, k, by accurately measuring the Doppler absorption profile of a line in a gas of ammonia at thermal equilibrium. This optical method based on the first principles of statistical mechanics is an alternative to the acoustical method which has led to the unique determination of k published by the CODATA with a relative accuracy of 1.7 ppm. We report on the first measurement of the Boltzmann constant by laser spectroscopy with a statistical uncertainty below 10 ppm, more specifically 6.4 ppm. This progress results from improvements in the detection method and in the statistical treatment of the data. In addition, we have recorded the hyperfine structure of the probed saQ(6,3) rovibrational line of ammonia by saturation spectroscopy and thus determine very precisely the induced 4.36 (2) ppm broadening of the absorption linewidth. We also show that, in our well chosen experimental conditions, saturation effects have a negligible impact on the linewidth. Finally, we draw the route to future developments for an absolute determination of with an accuracy of a few ppm., 22 pages, 11 figures

Collisions of S(1D) with CO, N2, O2, and CO2 have been investigated to estimate the fraction of the sulfur electronic energy that is deposited in the internal degrees of freedom in the collision partner during the quenching of S(1D) to S(3P). The experiment measures the Doppler profile of the S(3P) product, a profile that depends both on the amount of energy disposed into the internal degrees of freedom and on the differential scattering cross section for the inelastic collision. For CO and N2 the results are consistent with a collision complex model for which the scattering is assumed to be isotropic in the collision plane and for which the energy is partitioned statistically into the degrees of freedom. Under the assumption of isotropic scattering, the results suggest that less energy than the statistical prediction is partitioned into translation for collisions with O2, whereas more energy is partitioned into translation for CO2.

Perturbations in the 7(16) and 8(18) mixed singlet/triplet levels of ã (1)A(1)(0,0,0) methylene, CH(2), have been reinvestigated by frequency-modulated laser sub-Doppler saturation spectroscopy. The hyperfine structure was completely resolved for both the predominantly singlet and the predominantly triplet components of these mixed rotational levels using b̃ (1)B(1)-ã (1)A(1) optical transitions near 12 200 cm(-1) with megahertz resolution. The mixing coefficients were obtained from the observed hyperfine splittings and a two-level deperturbation model. The analysis also determines the energy separation of the unperturbed zero-order levels and the unperturbed hyperfine splittings for the triplet perturbing levels 6(15) X̃ (3)B(1)(0,3,0) and 9(37) X̃ (3)B(1)(0,2,0).

Alkyl chlorides (R=CH3, C2H5, C3H7, and C4H9), chloromethanes (CHnCl4−n), and chlorofluoromethanes (CFnCl4–n) are photodissociated at 157 and 193 nm. The chlorine atom photofragments are detected by a resonance enhanced multiphoton ionization technique. The branching ratios of the Cl photofragments [Cl*(3p2P1/2)]/[Cl(3p2P3/2)] are almost identical (0.23±0.03) for alkyl monochlorides at 157 and 193 nm and for CH2Cl2 and CHCl3 at 157 nm, while the ratios are rather small (0.10±0.02) for CH2Cl2 and CHCl3 at 193 nm. No discernible isotope effects on the branching ratios were observed when D atoms were substituted for H atoms in chloromethanes. For CCl4, CF3Cl, CF2Cl2, CFCl3 at 157 and 193 nm, the ratios are small (

International audience; We report on the measurement of the edge ion temperature in TJ-II plasmas, heated by electron cyclotron waves and neutral beam injection, using passive spectroscopy of impurity ions in low ionization stages. The measurements, which provide both temporal and some spatial resolution, offer some advantages over more intrusive or more sophisticated methods. The capabilities and limitations of this approach are illustrated by showing typical results obtained in conditions of interest for fusion plasmas. B Peláez et al, Probing the edge ion temperature by passive Doppler spectroscopy in the TJ-II... 2 1.

International audience; In this work we present an overview on the CXRS diagnostic operated with the modulated diagnostic hydrogen beam at the Tokamak TEXTOR. The diagnostic setup combines two observation systems used for the measurement of the poloidal (v pol) and the toroidal (v tor) ion velocity component. At TEXTOR a differential Doppler spectroscopy approach (accurate absolute rotation scale) is combined with the high intensity and spatial resolution of a direct imaging system necessary for accurate poloidal rotation measurements on a shot by shot basis. This setup allows the full utilization of the a 2D CCD detector in the spectral and radial direction. In case of the poloidal system this allows spatial resolution in the range of mm to cm depending on the intensity requirements for the velocity. The toroidal system is comprised of a fiber-optic array. The combination of the two measurements with a low power diagnostic beam can in principal be operated during any available heating scenario without interfering with the discharge. Time resolution is limited by the necessary averaging process, typically a stable plateau of 3 s during a TETXOR pulse is used. The TEXTOR tokamak has the ability to apply momentum input with two tangential neutral beam heating injectors, allowing for measurements under various heating and momentum input scenarios. With the presented diagnostic half the plasma minor radius at a spatial resolution of ∼ 1cm is covered. With the CVI line at 529.053 nm an accuracy of 0.7km/s for the poloidal and ∼ 5 km/s for the toroidal system is given. The temperature is measured with an accuracy of a few eV. The presented work illustrates the capability of the system during a toroidal momentum scan, showing the self-consistent determination of the radial electric field from experimental CXRS data based on the radial force balance.

An acoustic inversion technique, known as Geo‐Acoustic Doppler Spectroscopy, has recently been developed for estimating the geo‐acoustic parameters of the seabed in shallow water. The technique is unusual in that it utilizes a low‐flying, propeller‐driven light aircraft as an acoustic source. Both the engine and propeller produce sound and, since they are rotating sources, the acoustic signature of each takes the form of a sequence of narrow‐band harmonics. Although the coupling of the harmonics across the air‐sea interface is inefficient, due to the large impedance mismatch between air and water, sufficient energy penetrates the sea surface to provide a useable underwater signal at sensors either in the water column or buried in the sediment. The received signals, which are significantly Doppler shifted due to the motion of the aircraft, will have experienced a number of reflections from the seabed and thus they contain information about the sediment. A geo‐acoustic inversion of the Doppler‐shifted modes associated with each harmonic yields an estimate of the sound speed in the sediment; and, once the sound speed has been determined, the known correlations between it and the remaining geo‐acoustic parameters allow all of the latter to be computed. This inversion technique has been applied to aircraft data collected in the shallow water north of Scripps pier, returning values of the sound speed, shear speed, porosity, density and grain size that are consistent with the known properties of the sandy sediment in the channel.

Over the past 14 years, Doppler spectroscopy has been very successful in detecting and characterizing extrasolar planets, providing us with a wealth of information on these distant worlds (e.g., Marcy et al. 2005a; Udry and Santos 2007b; Udry et al. 2007a). One important and considerably unexpected fact these new data have taught us is that diversity is the rule in the planetary world. Diversity is found not only in the characteristics and orbital properties of the ∼ 340 planets detected thus far,1 but also in the types of environments in which they reside and are able to form. This observation has prompted a serious revision of the theories of planet formation (e.g., Lissauer and Stevenson 2007; Durisen et al. 2007; Nagasawa et al. 2007), leading to the idea that planet formation may be a richer and more robust process than originally thought.

Velocity relaxation of S(1D) by He, Ar, and Xe has been monitored by measuring the Doppler profile of the S(1D) for variable collision partner pressures at a fixed time delay following creation of S(1D) by pulsed laser photolysis of OCS at 222 nm. The nascent S(1D) has a mean speed about three times that at room temperature and an effective anisotropy parameter of β=0.5. A calculation assuming elastic hard‐sphere collisions is performed to model the process. The data are in qualitative agreement with the model in that the angular distribution relaxes more rapidly with collision number as the mass ratio between the collision partner and sulfur approaches infinity, whereas the speed distribution relaxes more rapidly as the mass ratio approaches one. Helium behaves as predicted by the hard‐sphere model with a collision cross section of σcol=26±2 A2. However, the cross sections for argon and xenon are found to depend on the collision energy. The dependence allows an estimation of the following Lennard‐Jones p...

Silane, germane, chlorosilanes, and chloromethanes are photodissociated at 157.6 nm. SiH 4 and GeH 4 are also photodissociated by a two-photon process at 243.1 nm. Hydrogen and chlorine atoms are detected using multiphoton ionization technique for measurement of Doppler profiles. The kinetic energy distribution of the nascent hydrogen atoms from silane and germane are derived from the Doppler profiles, which are Boltzmann

A simple and sensitive method combining ion imaging with Doppler spectroscopy has been developed to measure full three‐dimensional velocity distributions of low energy scattering particles. This technique was applied to the photolysis study of an HBr molecular beam at 243 nm.

The use of MeV ion beams to measure hydrogen concentration profiles is reviewed. Both nuclear reaction analysis (NRA) and energy recoil detection (ERD) methods are discussed. Details of experimental approaches used and the effects of these different approaches on the analytic characteristics obtained are considered. The use of Doppler spectroscopy in both NRA and ERD to study the bonding of hydrogen in solids is briefly reviewed. The different methods are compared in terms of their advantages and disadvantages for certain analytic characteristics including accuracy, beam damage effects, sensitivity, and depth resolution.

The goal of this investigation is to study, in the line of previous works, the level of velocity fluctuations in different scenarios of the TJ-II stellarator. The method followed consists in measuring the apparent Doppler temperature of C4+ and protons with high spectral resolution techniques with spatial resolution. The level of turbulent velocities in the plasma has been deduced from the difference observed between the apparent temperature of both species, following a method previously presented and borrowed from astrophysics. The study of this difference, as a function of plasma density and injected power, provides a way to explore if this turbulence plays any role in the confinement of the hot TJ-II plasma., 8 pages, 5 figures

Over 300 extrasolar planets have been found since 1992, showing that planetary systems are common and exhibit an outstanding variety of characteristics. As the number of detections grows and as models of planet formation progress to account for the existence of these new worlds, statistical studies and confrontations of observation with theory allow to progressively unravel the key processes underlying planet formation. In this chapter we review the dominant contribution of Doppler spectroscopy to the present discoveries and to our general understanding of planetary systems. We also emphasize the synergy of Doppler spectroscopy and transit photometry in characterizing the physical properties of transiting extrasolar planets. As we will see, Doppler spectroscopy has not reached its limits yet and it will undoubtly play a leading role in the detection and characterization of the first Earth-mass planets., Comment: 50 pages, 16 figures, to appear in the proceedings of the Les Houches Winter School "Physics and Astrophysics of Planetary Systems" (EDP Sciences: EAS Publications Series)

Several new experimental results are reported from plasma merging studies at the Swarthmore Spheromak Experiment (SSX) with relevance to collisionless three‐dimensional magnetic reconnection in laboratory and space plasmas. First, recent high‐resolution velocity measurements of impurity ions using ion Doppler spectroscopy (IDS) show bi‐directional outflow jets at 40 km/s (nearly the Alfven speed). The SSX IDS instrument measures with 1 μs or better time resolution the width and Doppler shift of the CIII impurity (H plasma) 229.7 nm line to determine the temperature and line‐averaged flow velocity during spheromak merging events. High flow speeds are corroborated using an in situ Mach probe. Second, ion heating to nearly 106 K is observed after reconnection events in a low‐density kinetic regime. Transient electron heating is inferred from bursts on a 4‐channel soft x‐ray array as well as vacuum ultraviolet spectroscopy. Third, the out‐of‐plane magnetic field and the in‐plane Lorentz force in a reconnectio...

The visible absorption spectrum of NO2 is so dense that many lines overlap within their Dopplerwidth. Sub-Doppler resolution is therefore demanded to completely resolve the spectrum in order to gain more information about the excited electronic states and their mutual interaction. This paper describes such measurements with greatly reduced Doppler width in a molecular beam. Different argon laser lines are used for selective excitation of various hyperfine structure levels. The fluorescence from these levels is monitored to investigate the radiative and radiationless decay channels of the excited NO2-molecules under collision free conditions.

A supersonically expanding arc plasma in argon is analyzed both experimentally and theoretically. The plasma is created in a cascaded arc and extracted through a hole in the anode. It emanates in a large vacuum system, where it expands supersonically. This expansion is limited by a shock wave. After the shock wave a subsonic plasma beam is created. A quasi one-dimensional model, based on the conservation of mass, momentum and energy is presented. The shock wave is treated as a discontinuity. The electron density, the gas velocity and the gas temperature are measured as a function of the position in the expansion by means of Stark broadening and Doppler spectroscopy. The model calculations agree well with the measurements, especially in the first part of the supersonic flow.

In the late 1980s, Dixon, Hall, Houston, Simons, and others recognized that experiments that probe the angular distribution of photofragments with spectroscopic techniques could be used to obtain the angular distribution of angular momentum polarization. These were generalized as “vector correlation” experiments, wherein one examines the correlations among the angular momentum polarization vector, the product recoil direction, the transition moment in the parent molecule, the laser polarization, the fluorescence polarization, or in scattering experiments, the relative velocity vector. Virtually all of the early studies were based on Doppler spectroscopy and emphasized rotational angular momentum polarization. Semiclassical models were used to interpret the experiments, largely, based on the bipolar harmonics approach introduced by Dixon. Around the same time, Chandler and Houston introduced the ion-imaging technique, in which the full recoil velocity distribution of stateresolved photofragments could be detected in a highly multiplexed approach. Soon thereafter, large orbital alignment effects in atoms were seen in imaging experiments, and it was immediately recognized that the semiclassical picture, developed to describe high-J rotational polarization, would not be suitable for interpretation of angular momentum polarization in atoms, and a new, fully quantum theory was required. The foundation for this theory was established in a paper in 1994 by Siebbeles et al. (see also the earlier paper by Vasyutinskii). The development of the theory is described fully in section 2.

In the late 1980s, Dixon, Hall, Houston, Simons, and others recognized that experiments that probe the angular distribution of photofragments with spectroscopic techniques could be used to obtain the angular distribution of angular momentum polarization. These were generalized as “vector correlation” experiments, wherein one examines the correlations among the angular momentum polarization vector, the product recoil direction, the transition moment in the parent molecule, the laser polarization, the fluorescence polarization, or in scattering experiments, the relative velocity vector. Virtually all of the early studies were based on Doppler spectroscopy and emphasized rotational angular momentum polarization. Semiclassical models were used to interpret the experiments, largely, based on the bipolar harmonics approach introduced by Dixon. Around the same time, Chandler and Houston introduced the ion-imaging technique, in which the full recoil velocity distribution of stateresolved photofragments could be detected in a highly multiplexed approach. Soon thereafter, large orbital alignment effects in atoms were seen in imaging experiments, and it was immediately recognized that the semiclassical picture, developed to describe high-J rotational polarization, would not be suitable for interpretation of angular momentum polarization in atoms, and a new, fully quantum theory was required. The foundation for this theory was established in a paper in 1994 by Siebbeles et al. (see also the earlier paper by Vasyutinskii). The development of the theory is described fully in section 2.

We experimentally demonstrate two methods that improve the resolution of sub-Doppler spectroscopy using a 1 mm thick vapor cell. The linewidths of the observed spectra are approximately 1 order of magnitude narrower than the Doppler width. The first method involves using a 1 mm thick cell filled with Rb atomic vapor and two spatially separated laser beams. By employing the same principle, we also demonstrate that it is possible to achieve the same resolution by using the pump and probe pulses of a single beam. The latter method enables us to construct a simple and robust optical setup for sub-Doppler spectroscopy.

We describe an alternative approach for a reliable lifetime prediction employing the local concentration of lattice defects as a precursor for fatigue failure. We present positron annihilation spectroscopy (PAS) as a non-destructive technique sensitive for defect concentrations in the range relevant to plasticity in metals.

A general method is developed for determination of cylindrically symmetric velocity distributions from Doppler profile measurements. This method applies Kinsey’s Fourier transform Doppler spectroscopy [J. L. Kinsey, J. Chem. Phys. 66, 2560 (1977)] to distributions arising from photodissociation and uses an orthogonal polynomial expansion to perform the integral transforms analytically. This method is shown to offer an improvement in stability over direct numerical solution of the integral equation and to have applicability to distributions which are not ‘‘separable,’’ that is, which cannot be separated into a product of speed‐ and angle‐dependent factors. The method is applied to experimental measurements of the collisional relaxation of a fast anisotropic distribution of I[2P1/2] atoms in a thermal bath (preceding paper). It is shown that the nascent distribution is separable, but the distribution does not remain separable throughout the relaxation process.

The paper is the review of methods, achievements, and possibilities of the recently elaborated and well tested high-resolution laser spectroscopy based on sub-Doppler absorption and polarization resonances (on centers of quantum transitions), which arise because of the optical pumping and specific transit relaxation of atoms (molecules) in a thin cell with a rarefied gas. Theoretical basis of this spectroscopy is presented. Experimental technique and results on the record of the sub-Doppler spectral structure of Cs and Rb atoms and on the frequency stabilization of diode lasers by given spectroscopy methods are discussed.