High-resolution Spectroscopy Techniques Research Articles

Approach to the physical origin of breakdown in silicon solar cells by optical spectroscopy

The electrical breakdown of silicon solar cells at low reverse currents has recently gained increased attention. In this study we investigate the physical properties of prebreakdown sites with high resolution spectroscopy techniques. These techniques comprise the measurement of the electroluminescence under reverse voltage, microphotoluminescence spectroscopy, and micro-Raman spectroscopy. The measurements show very high levels of stress at the prebreakdown sites, an increase in the breakdown size with applied reverse bias and redshift in the breakdown electroluminescence spectrum with increasing onset voltage. The results are tentatively explained by a lower bandgap energy at the breakdown sites, which could be caused by stress.

Doppler-free polarization spectroscopy with a quantum cascade laser at 43 µm

We report on what we believe to be the first Doppler-free polarization spectroscopy with a quantum cascade laser. A hot-band CO(2) transition around 4.3 microm wavelength has been used to test the potential of the technique for high-resolution spectroscopy and wide-bandwidth quantum cascade laser frequency stabilization.

CHAPS: a new precision laser-spectroscopic technique

We present a new technique for high-resolution pulsed spectroscopy that employs optical heterodyne detection to determine the instantaneous frequency of individual optical pulses, together with a frequency-binning method to generate high-precision spectra. We further demonstrate that active tuning of the light source is not necessary if the inherent frequency jitter of the source spans the spectral region of interest. This heterodyneassisted approach to coherent pulsed spectroscopy (CHAPS) is applied in real time by using output from a pulsed, injection-seeded optical parametric oscillator–amplifier (OPO–OPA) system, the optical bandwidth of which is characterized via two-photon excitation of the 6S–8S transition in cesium. The resulting sub-Doppler measurements demonstrate the utility of CHAPS as a high-resolution spectroscopic technique and confirm that the pulsed OPO–OPA system operates very close to the Fourier-transform limit. © 2006 Optical Society of America OCIS codes: 020.4180, 040.2840, 120.6200, 190.4970, 230.4320, 300.3700, 300.6320, 300.6410.

Spectroscopy of the R-system (1 8 0) group band of CS 2 achieved by Λ-type excitation

We have demonstrated a high resolution spectroscopic technique, the so-called Λ-type excitation, to re-investigate (1 8 0) group band of CS 2, which is closely located below the barrier of bent to linear. Λ-type excitation is a three-photon process. Rotationally resolved spectroscopy can be achieved as long as the chosen intermediate state can be rotationally resolved. Applying this technique, we are able to resolve the doublet due to the complexity of the potential near the bent-to-linear barrier top. And due to gaining a favorable Frank–Condor factor from the initial state (3 18 0), instead of (0 0 0), a combination mode having 2 ν 3 excitation induced by ν 2 mode Coriolis interaction was observed as well.

NiO as a test case for high resolution resonant inelastic soft x-ray scattering

Resonant inelastic x-ray scattering (RIXS) at theL2,3 edgesof 3d transition metal compounds has recently become a high resolution spectroscopictechnique thanks to improvements in the instrumentation. We have chosen theprototypical case of NiO to explore the various levels of interpretation applicable toL3 RIXSspectra of strongly correlated electron systems. Starting from a set of experimental data measured acrossthe Ni L3 absorption edge with 550 meV combined energy resolution, we analyse the richspectral structure within an atomic framework. The spectra can be separated intodd and charge transferexcitation regions. The dd excitations can be interpreted and well reproduced within a crystal field model. The chargetransfer excitations are analysed through the comparison with calculations made in theAnderson impurity model. A series of parameters belonging to the proposed models(crystal field strength, charge transfer energy, hybridization integrals) can thus be extractedin a very direct and unambiguous way.

A new digital auto-tracking pole-zero compensation technique for high-resolution spectroscopy

In order to obtain high-energy resolution in both analogue and digital spectroscopy systems, it is mandatory to guarantee the stability of the baseline signal reference. The precision of the compensation of the long exponential decay due to the charge preamplifier, especially in case of high rate of events, has a direct influence on the baseline reference value. We have developed a new technique, which automatically performs such a compensation on-line in a digital way. It allows obtaining spectroscopic performance and keeps at minimum both the A/D converter sampling frequency (thus power consumption) and its resolution (thus cost). This is done through a fixed-point processing architecture, which is implemented within a FPGA device. During operation, the compensator automatically tracks variations of the value of the preamplifier time constant also at high event rate.

Micro-particles temperature measurements in a plasma jet

A high spatial resolution spectroscopic technique was developed for temperature measurements of micro-particles heated in a plasma jet. The knowledge of the particles temperature distribution was used to optimize the plasma spraying process.

Characteristics of a successful space system engineer

The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite was launched on June 24, 1999, on a three-year mission to explore the universe using the technique of high-resolution spectroscopy in the far-ultraviolet spectral region. The FUSE instrument comprises many subsystems, each of which contributes in an essential way to the success of the mission. The instrument system engineer oversees the engineering of all elements in such a complex technical project. In performing system engineering for the FUSE instrument's command, telemetry, data processing and data storage functions, and in leading the engineering efforts for the development of the FUSE instrument on-board computer, the author has learned valuable lessons about the characteristics that are prerequisite to success for a space system engineer. These characteristics fall under various categories of acquired, practical know-how. These categories are described with illustrations drawn from the development of the FUSE instrument. In addition to these practical skills and the concomitant knowledge, the system engineer needs personal integrity, which is the link that connects knowledge with know-how and makes them work together to motivate a team of subsystem engineers. This, too, will be discussed.

The angle-resolved Kr L2,3M4,5M4,5 Auger multiplet following proton impact ionization

The angle-resolved Kr L2,3M4,5M4,5 Auger spectra induced by proton impact ionization were measured at 1, 2.6 and 3.6 MeV proton energies where high-resolution spectroscopy techniques have been applied. The Auger energies and relative line intensities are compared with different earlier experimental data as well as our numerical results which have been obtained within a multiconfigurational Dirac-Fock approach. The alignment parameter 20 of the singly ionized krypton atoms has been extracted from the experimentally accessible anisotropy parameter A2 applying a special method, using the theoretical values of the angular distribution parameter 2 .

The Feynman path integral approach to atomic interferometry. A tutorial

Many problems of current interest in interferometry lend themselves to a path integral treatment. We present a practical guide to solving such problems, taking as examples the gravitational experiments of Kasevich and Chu, and the equivalents of the Sagnac and Aharonov-Bohm effects. Atomic interferometry is a new and rapidly-developing field of research, concerned with physical phenomena in which the wave-nature of neutral atoms plays an important role ill. The wide variety of internal degrees of freedom of an atom opens up new possibilities for investigation which do not exist in the more traditional types of interferometry using photons, electrons and neutrons. The development of interferometry has been aided by recent technical advances, particularly in the manipulation of atoms. New mechanisms for slowing, deflecting, cooling and trapping atoms allow control of both their position and momentum. Also important has been the birth of atomic optics, a range of mechanisms providing the equivalent of mirrors, beamsplitters and lenses for atoms. Recently it has been pointed out that certain high-resolution spectroscopy techniques which avoid the Doppler effect amount to realizing an interferometer (2). These methods have since been adapted to measure inertial fields (due to rotation and gravitation) by interferometry. The situation encountered in interferometry experiments is often close to the classical limit. When this is the case a path integral approach to the analysis is very appropriate since it reduces to a calculation of integrals along classical paths. Further simplifications can be made if the Lagrangian is quadratic, as is true for a particle in a gravitational field or a rotating (*) The Laboratoire Kastler Brossel is associated with the CNRS and the Universit4 Pierre et Marie

Sub-Doppler UV spectroscopy by resonance-enhanced two-photon ionization: the structure of the benzene 20,22Ne cluster

In this work it is demonstrated that mass selected multiphoton ionization is a powerful technique for high resolution spectroscopy, isotope cluster separation and investigation of the structure of van der Waals clusters. The rotationally resolved UV spectra of the benzene- 20Ne and benzene- 22Ne clusters are selectively measured in a natural isotopic mixture of benzene and benzene-Ne clusters in a cooled supersonic jet. The analysis of these spectra yields accurate values for the rotational constants of both species. From this data it is found that the Ne atom is located on the C 6 rotational axis of the benzene ring at an average distance of 3.46Åwith a slight difference for the two isotopes. This distance decreases by 40 mÅwhen benzene is electronically excited. The influence of the large amplitude van der Waals vibrations on the average bond length is discussed.

X-ray optics 2: A technique for high resolution spectroscopy

A novel combination of optical elements and properties is combined to achieve high spectral resolution using grazing incidence optics of modest quality. We show through analysis and ray tracing of examples that using radial groove gratings at high blaze angles in the manner of an echelle spectrograph can provide high spectral resolution. We compare this arrangement to the conventional in-plane designs and show the off-plane to be superior in nearly every respect. Cross dispersion can be provided by the energy resolution of a CCD detector. Then, we show how additional resolution can be squeezed from the system by strategic placement of gratings to take advantage of the azimuthal response of a Wolter x-ray optic. With a telescope that has only 30-sec of arc imaging we are able to support resolution lambda/deltalambda of 3000, while a conventional design at the same graze angle supports resolution of only 200.

Tunable far infrared laser spectroscopy of ultracold free radicals

We report a new high-resolution spectroscopic technique designed for the study of short-lived free radicals and clusters containing free radicals. Excimer laser photolysis of a suitable precursor during the initial stages of a planar supersonic expansion is used to generate ultracold free radicals which are subsequently probed by a tunable far infrared laser. A detection limit of 10 8 molecules/cm 3 for light hydrides is demonstrated and prospects for 2 to 3 orders of magnitude improvement are discussed.

Thermoluminescence of the lunar surface

Observations of the lunar luminescence are reported for a dozen of specific Moon features using the ‘line-depth’ method with a high resolution spectroscopic technique. The data indicate a variation of the Moon proper emission as a function of the phase angle which is interpreted as a proof of the thermoluminescent origin of this emission.

Optical analysis of the hyperfine structure of ^59Co in the region 4000–4300 Å

The hyperfine structure of several lines of the spectrum of cobalt between 4000 and 4300 Å has been analyzed using the technique of high-resolution spectroscopy. As a result, the value of the magnetic hyperfine structure constant for 32 states has been found. The classification for four of the lines has also been inferred from the observed hyperfine structure patterns.

A novel and sensitive technique for high resolution spectroscopy

A novel and sensitive technique for high resolution spectroscopy

Resonance 2.7 eV above theNi64(p,n1)Cu*64threshold

Time of flight spectra of near threshold neutrons from the $^{64}\mathrm{Ni}(p,{n}_{1})^{64}\mathrm{Cu}^{*}$ reaction clearly show the presence of a ${\frac{5}{2}}^{+}$ resonance which is located 2.7 eV above the 2.67-MeV threshold. Its total width is 5 eV and its peak cross section is 14 mb. Through this study one deduces the basic limitation on the technique of high resolution spectroscopy very near reaction thresholds. Very near neutron thresholds, because a number of kinematic factors conspire in a favorable way, one can achieve the equivalent of slow-neutron resolution even though the neutrons are not slow. We know of no other technique which would allow individual study of such resonances.NUCLEAR REACTIONS $^{64}\mathrm{Ni}(p,{n}_{1})^{64}\mathrm{Cu}^{*}$, near threshold; measured neutron spectra. Deduced resonance parameters of the first resonance above threshold. Deduced basic limitations on the near threshold technique.