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We used a sample of super-Earth-like planets detected by the Doppler spectroscopy and transit techniques to explore the dependence of orbital parameters of the planets on the metallicity of their host stars. We confirm the previous results (although still based on small samples of planets) that super-Earths orbiting around metal-rich stars are not observed to be as distant from their host stars as we observe their metal-poor counterparts to be. The orbits of these super-Earths with metal-rich hosts usually do not reach into the Habitable Zone (HZ), keeping them very hot and inhabitable. We found that most of the known planets in the HZ are orbiting their GK-type hosts which are metal-poor. The metal-poor nature of planets in the HZ suggests a high Mg abundance relative to Si and high Si abundance relative to Fe. These results lead us to speculate that HZ planets might be more frequent in the ancient Galaxy and had compositions different from that of our Earth., Comment: Accepted for OLEB special issue. Editors: Muriel Gargaud, Nigel Mason, and Wolf Geppert

Characterizing the atmospheres of extrasolar planets is the new frontier in exoplanetary science. The last two decades of exoplanet discoveries have revealed that exoplanets are very common and extremely diverse in their orbital and bulk properties. We now enter a new era as we begin to investigate the chemical diversity of exoplanets, their atmospheric and interior processes, and their formation conditions. Recent developments in the field have led to unprecedented advancements in our understanding of atmospheric chemistry of exoplanets and the implications for their formation conditions. We review these developments in the present work. We review in detail the theory of atmospheric chemistry in all classes of exoplanets discovered to date, from highly irradiated gas giants, ice giants, and super-Earths, to directly imaged giant planets at large orbital separations. We then review the observational detections of chemical species in exoplanetary atmospheres of these various types using different methods, including transit spectroscopy, doppler spectroscopy, and direct imaging. In addition to chemical detections, we discuss the advances in determining chemical abundances in these atmospheres and how such abundances are being used to constrain exoplanetary formation conditions and migration mechanisms. Finally, we review recent theoretical work on the atmospheres of habitable exoplanets, followed by a discussion of future outlook of the field., Comment: Accepted for publication in Space Science Reviews. Chapter in International Space Science Institute (ISSI) Book on "The Disk in Relation to the Formation of Planets and their Proto-atmospheres" to be published in Space Science Reviews by Springer

Doppler spectroscopy was the first technique used to reveal the existence of extrasolar planetary systems hosted by solar-type stars. Radial-velocity surveys led to the detection of a rich population of super-Earths and Neptune-type planets. The numerous detected systems revealed a remarkable diversity. Combining Doppler measurements with photometric observations of planets transiting their host stars further provides access to the planet bulk density, a first step towards comparative exoplanetology. The development of new high-precision spectrographs and space-based facilities will ultimately lead us to characterize rocky planets in the habitable zone of our close stellar neighbours.

Velocity of hydrogen plasmas rotating due to imposed E × B fields at the Maryland Centrifugal Experiment (MCX) (Ellis et al., Phys Plasmas 12:055704, 2005), where E is the electric field in the radial direction and B the magnetic field in the axial direction of a cylindrical configuration, has traditionally been measured using Doppler shifts of atomic spectra from impurity elements such as carbon. Ideally, the gyrocenter of trace particles rotates at the bulk plasma velocity, regardless of the charged state or trace particle mass. However, for sufficiently large applied |E/B| (or equivalently, a sufficiently large ratio of bulk plasma rotation frequency and particle gyrofrequency), charged particles may have gyroradii that depart significantly from quasi-circular orbits drifting about the B field axis. This effect is investigated numerically with a single particle code that includes scattering, as well as experimentally at MCX. Numerical findings are compared to experimentally measured Doppler shifts of singly inonized helium and oxygen, and doubly ionized carbon atoms.

We report several new experimental results related to flow dynamics and heating from single dipole-trapped spheromaks and spheromak merging studies at SSX. Single spheromaks (stabilized with a pair of external coils, see Brown, Phys. Plasmas 13 102503 (2006)) and merged FRC-like configurations (see Brown, Phys. Plasmas 13, 056503 (2006)) are trapped in our prolate (R = 0.2 m, L = 0.6 m) copper flux conserver. Local spheromak flow is studied with two Mach probes (r 1 ≤ ρ i , r 2 ≥ ρ i ) calibrated by time-of-flight with a fast set of magnetic probes at the edge of the device. Both Mach probes feature six ion collectors housed in a boron nitride sheath. The larger Mach probe will ultimately be used in the MST reversed field pinch. Line averaged flow is measured by ion Doppler spectroscopy (IDS) at the midplane. The SSX IDS instrument measures with 1 μs or better time resolution the width and Doppler shift of the C III impurity (H plasma) 229.7 nm line to determine the temperature and line-averaged flow velocity (see Cothran, RSI 77, 063504 (2006)). We find axial flows up to 100 km/s during formation of the dipole trapped spheromak. Flow returns at the wall to form a large vortex. Recent high-resolution IDS velocity measurements during spheromak merging show bi-directional outflow jets at ±40 km/s (nearly the Alfven speed). We also measure T i ≥ 80 eV and T e ≥ 20 eV during spheromak merging events after all plasma facing surfaces are cleaned with helium glow discharge conditioning. Transient electron heating is inferred from bursts on a four-channel soft x-ray array. The spheromaks are also characterized by a suite of magnetic probe arrays for magnetic structure B(r,t), and interferometry for n e . Finally, we are designing a new oblate, trapezoidal flux conserver for FRC studies. Equilibrium and dynamical simulations suggest that a tilt-stable, oblate FRC can be formed by spheromak merging in the new flux conserver.

A new experiment is under development for the study of turbulence, flow, and cross-field transport in a field-reversed configuration. The facility is a merged-spheromak device driven by magnetized coaxial plasma guns. Experimental emphasis is given to advanced diagnostic development, including high spatial resolution and high time resolution instruments for measurement of fluctuating quantities and bulk velocity in high beta plasmas. Instruments at various stages of development include a multichord quadrature CO2 interferometer, a multichannel Mach-probe array, a multifrequency reflectometry system, a multi-point Doppler spectroscopy probe, and a number of magnetic diagnostics. Technical details of the experimental facility and planned studies are described.

A continuous-wave mid-IR diode-laser-based, dual-cavity difference-frequency spectrometer employing silver thiogallate (AgGaS2) as the down-conversion material, and producing only 30 nW of usable mid-IR output, is used to record Doppler spectra of NH3 and SF6 around 10.2 μm and 10.5 μm over the 90-GHz range. The tuning procedure of the spectrometer as well as a baseline noise cancellation technique based on analogue signal ratioing are described. The device can potentially be used for ultra-high-resolution saturation spectroscopy, pending an improvement of the down-conversion efficiency to 1-μW power.

An inversion method for ion Doppler shift of spectrum lines was developed for plasma velocity measurements. By reducing the problem to the vectorial Radon transform, the characteristics of plasma ion velocity distribution such as vector potential/vorticity and velocity components were computed in two-dimensional space. Computer simulation of the reconstruction of different vector potential (vector field) models gives evidence that the reconstruction errors are acceptable, and the method can surely be used for real experimental data.

We performed saturated-absorption spectroscopy of H218O at 1.4 μm, using a low-power mirror-extended distributed-feedback diode laser. Although the rotational lines of the ν1+ν3 band investigated in this work had a small transition dipole moment, saturation was possible thanks to a short Fabry–Perot cavity with a finesse of about 500. We investigated the sub-Doppler spectrum of the 212→111 line for different sample gas pressures. A pressure-broadening coefficient of 32.9±0.7 MHz/Torr was measured. We also evaluated the saturation intensity as well as the transition dipole moment. To our knowledge, the observed Lamb dip represents the first narrow resonance at 1.4 μm.

The experimental determination of the radial electric fieldEr and the associatedE ×B drift velocity at the edge of RFX is presented and possible mechanisms responsible for its generation are discussed.Er measurements by means of an array of Langmuir probes and those deduced from Doppler spectroscopy of impurity lines agree fairly well. In particular the rotation velocity of the plasma edge has been determined from the Doppler shift of a C III emission line. The observation of other ions characterised by different radial positions, such as B IV and C V, has allowed an estimate of the velocity shear. Typical values of plasma rotation at the edge are around 10 km/s while the velocity shear is of the order of (105−106)s−1 in the spontaneous layer, a few cm thick, usually observed in standard discharges. Plasma rotation has been artificially modified by both positive and negative edge biasing and the associated increase or decrease of the fluid velocity is well in agreement with the radial electric field change. The modification ofEr during edge biasing and Pulsed Poloidal Current Drive (PPCD) are also reported and interpreted within a momentum balance model. Analytical and self-consistent Monte Carlo models at the plasma edge suggest that impurities have a relevant role in the generation of the radial electric field, due to their relatively large Larmor radius.

The energy spread of atomic and molecular ion beams from the 4 MV Dynamitron tandem accelerator at the Ruhr-Universitat Bochum has been studied and in part minimized. Using the ER= 6.40 MeV narrow resonance in 1H(15N,αγ)12C with an 15N energy spread of 4.55 keV, the Doppler broadening for several hydrogen-bearing gases was found to be in good agreement with expectation: e.g. for NH3 gas a rotational-vibrational Doppler width of 10.41 ± 0.25 keV was observed (theory = 10.4 keV). Studies of the vibrational Doppler widths of H-bonds on a Si surface were performed using a 4πγ-ray detection system together with UHV-chambers for sample preparation, transport, and analysis. The results showed that further improvements in the experimental set-ups are needed for such investigations.

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.

Improved molecular constants for the and states of the NaH molecule are presented. NaH molecules are produced by reactive scattering of H and Na2 in a crossed beam experiment. High vibrational levels (6 9) of the NaH molecules are predominantly populated. Their excitation spectrum in the range has been measured using a new variant of Doppler spectroscopy. The transition frequencies involving the vibrational levels 2 8 in the and 6 9 in the state have been determined with an accuracy of better than . Using also previously published data a new set of molecular constants for the and state is derived. In particular, the vibrational dependence of the rotational constants B, D and H as well as some of v”-v' band origins for and is determined. The transition frequencies measured here or published previously are reproduced by these new coefficients with an accuracy of 0.1 cm-1 [rms value] with a maximum deviation of 0.4 cm-1. New RKR potential energy curves have been calculated up to the turning points of the levels v” = 9 in the state and v' = 25 in the state.

A new method involving Doppler spectroscopy with laser techniques is proposed to observe bound-state β-decay of tritium. This process, although theoretically expected to occur, has not yet been observed. The proposed method is, in principle, capable of exposing a finite mass of the neutrino. The low source temperatures and laser spectroscopic resolution necessary for a neutrino mass measurement, although extremely difficult to achieve, appear accessible with conceivable advances of these techniques.

Laser induced fluorescence Doppler spectroscopy has been applied for the first time to atomic hydrogen using tunable VUV light at the Lyman-α line. The dissociation of HI at 266 nm into H+I(P 1/2) and H+I(P 3/2) has been investigated. The recoil energy, angular distribution and branching ratio of the H atom have been measured, serving to test and study the feasibility and applicability of the technique.