共查询到20条相似文献,搜索用时 109 毫秒
1.
V. Lupei A. Lupei N. Pavel T. Taira A. Ikesue 《Applied physics. B, Lasers and optics》2001,73(7):757-762
A high-resolution spectroscopic and emission-decay investigation of highly concentrated Nd:YAG single crystals and ceramics
shows that the state of the Nd3+ ions and their interaction in these materials are similar and can be used for construction of efficient solid-state lasers
directly pumped in the emitting level. This possibility is demonstrated by continuous-wave emission of concentrated Nd:YAG
crystals with up to 3.5 at. % Nd and ceramics with up to 6.8 at. % Nd under resonant 885-nm end pump.
Received: 28 May 2001 / Final version: 17 August 2001 / Published online: 10 October 2001 相似文献
2.
G. de Angelis T. Martinez A. Gadea N. Marginean E. Farnea E. Maglione S. Lenzi W. Gelletly C.A. Ur D.R. Napoli Th. Kroell S. Lunardi B. Rubio M. Axiotis D. Bazzacco A.M. Bizzeti Sona P.G. Bizzeti P. Bednarczyk A. Bracco F. Brandolini F. Camera D. Curien M. De Poli O. Dorvaux J. Eberth H. Grawe R. Menegazzo G. Nardelli J. Nyberg P. Pavan B. Quintana C. Rossi Alvarez P. Spolaore T. Steinhart I. Stefanescu O. Thelen R. Venturelli 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):51-55
Gamma ray transitions de-exciting states in the N = Z nucleus 70Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level
scheme of 70Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric
analogue states in 70Br and 70Se show a deviation from the expected behaviour which could be related to dripline effects.
Received: 18 July 2001 / Accepted: 25 September 2001 相似文献
3.
J. Zhang L. Zhang X. Peng X. Wang 《Applied Physics A: Materials Science & Processing》2001,73(6):773-775
MgO nanobelts have been fabricated by chemical vapor deposition using MgCl3 as starting material. The products consist of a large quantity of belt-like nanostructures with typical lengths in the range
of several tens to several hundreds of micrometers; some of them even have lengths on the order of a millimeter. The typical
thickness and width-to-thickness ratio of the MgO nanobelts are in the range of 20 to 100 nm and about 5 to 10, respectively.
The size and morphology of the MgO nanobelts were measured by transmission electron microscopy. Investigations of X-ray diffraction
patterns and using high-resolution transmission electron microscopy indicate that the nanobelts have a cubic structure and
are single-crystalline.
Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 2 October 2001 相似文献
4.
Bias-, frequency- and temperature-dependent capacitance characteristics of p-GaAs homojunction interfacial work-function internal
photoemission (HIWIP) far-infrared detectors are reported. A strong negative capacitance phenomenon has been observed. The
origin of this effect is believed to be due to the carrier capture and emission at interface states, and has been confirmed
by a comparison study of capacitance characteristics on p-GaAs HIWIP detectors with different interface state densities. A
fitting data based on charging–discharging current and the inertial conducting current model show good agreement with the
experimental observations.
Received: 15 November 1999 / Accepted: 20 April 2000 / Published online: 5 October 2000 相似文献
5.
X.H. Zhou Y. Zheng Y.H. Zhang Z. Liu Q.Y. Pan Z.G. Gan T. Hayakawa M. Oshima T. Toh T. Shizuma J. Katakura Y. Hatsukawa M. Matsuda H. Kusakari M. Sugawara K. Furuno T. Komatsubara 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):253-255
The high-spin states of 145Tb have been studied in the 118Sn(32S, 1p4n) reaction at 32S energies from 161 to 175 MeV using techniques of in-beam γ-ray spectroscopy. Measurements of γ-ray excitation functions
and γ-γ-t coincidences were performed with 12 BGO(AC)HPGe detectors. Based on the measured results of γ-γ coincidences, γ-ray anisotropies
and DCO ratios, a level scheme for 145Tb was established for the first time. The observed excited states show typical irregular pattern in a spherical nucleus,
and the low-lying levels have been interpreted qualitatively with a particle-core coupling.
Received: 21 September 2001 / Accepted: 9 November 2001 相似文献
6.
BARC has developed large-area silicon detectors in collaboration with BEL to be used in the pre-shower detector of the CMS
experiment at CERN. The use of floating guard rings (FGR) in improving breakdown voltage and reducing leakage current of silicon
detectors is well-known. In the present work, it has been demonstrated that FGRs can also be used to improve the spectroscopic
response of silicon detectors. The results have been confirmed by carrying outα-particle (≈5 MeV) andγ-ray (60 keV) spectroscopies with the FGR floating or biased and the underlying physics aspect behind the change in spectra
is explained. Although reduction in leakage current after biasing one of the guard rings has been reported earlier, the role
of a guard ring in improving the spectroscopic response is reported for the first time. Results of TCAD simulations for silicon
detectors with the guard ring under different biasing conditions have been presented. Low yield in producing large-area silicon
detectors makes them very costly. However, with one of the FGRs biased even a detector having large surface leakage current
can be used to give the same response as a very good detector. This makes the use of large-area silicon detectors very economical
as the yield would be very high (>90%). 相似文献
7.
K. Vetter 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):265-269
Gamma-ray tracking in a closed array of highly segmented HPGe detectors is a new concept for the detection of γ-radiation.
Each of the interacting γ-rays is identified and separated by measuring the energies and positions of individual interactions
and by applying tracking algorithms to reconstruct the scattering sequences, even if many γ-rays hit the array at the same
time. The three-dimensional position and the energy of interactions are determined by using two-dimensionally segmented Ge
detectors along with pulse-shape analysis of the signals. Such a detector will have new and much improved capabilities compared
to current γ-ray spectrometer. One implementation of this concept, called GRETA (Gamma-Ray Energy Tracking Array), is currently
being under development at LBNL.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: kvetter@lbl.gov 相似文献
8.
K.W. Schmid 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):29-40
The mathematical tools to restore Galilei invariance in the nuclear many-body problem with the help of projection techniques
are presented. For simple oscillator configurations recursion relations for the various elementary contractions are derived.
The method is then applied to simple configurations for the ground states of 4He, 16O and 40Ca as well as to the corresponding one-hole and one-particle states. As a first application the spectral functions and spectroscopic
factors for the above-mentioned doubly even nuclei are investigated. It turns out that the conventional picture of an uncorrelated
system underestimates the single-particle strengths of the hole states from the last occupied shell while that of the higher
excited hole states is overestimated considerably. These results are in complete agreement with those derived by Dieperink
and de Forest using different methods. Similar effects are seen for the particle states which have not been studied before.
All the calculations presented here are performed analytically and thus can be checked explicitly by the interested reader.
Received: 20 February 2001 / Accepted: 11 September 2001 相似文献
9.
S. Gulde D. Rotter P. Barton F. Schmidt-Kaler R. Blatt W. Hogervorst 《Applied physics. B, Lasers and optics》2001,73(8):861-863
We report a simple and efficient method to load a Paul trap with Ca+ ions. A beam of neutral atomic calcium is ionized in a two-step photo-ionization process using uv-diode lasers near 423 nm
and 390 nm. Photo-ionization of a calcium beam for loading a Paul trap has first been demonstrated by Kjaergaard et al. The
advantages of our method are the use of cheap and easily handled diode-laser systems and the large cross section for field
ionization when exciting high-lying Rydberg states. Finally, we discuss the advantages of photo-ionization for ion generation
compared to loading by electron bombardment.
Received: 24 August 2001 / Revised version: 16 October 2001 / Published online: 23 November 2001 相似文献
10.
M. Sveningsson R.-E. Morjan O.A. Nerushev Y. Sato J. Bäckström E.E.B. Campbell F. Rohmund 《Applied Physics A: Materials Science & Processing》2001,73(4):409-418
Carbon-nanotube films are very efficient cathodes for field-emission devices. This study presents a comprehensive comparison
between structural, spectroscopic and field-emission properties of films of aligned and non-aligned multi-wall nanotubes (MWNTs)
which are grown by thermal chemical vapour deposition. Three types of films are investigated: vertically aligned MWNTs with
clean and coated nanotube side walls as well as non-aligned MWNT films. Raman spectra taken on the aligned MWNT films consist
of many lines of first-, second- and third-order signals. Several lines are reported here for the first time for MWNTs. The
presence of the surface coating leads to a decrease and broadening of the higher-order signals as well as an increase in the
disorder-induced contributions in the first-order regime. The aligned MWNT films have excellent field-emission properties
with very high emission current densities and low turn-on and threshold fields. The presence of a surface coating has no impact
on the efficiency of the field-emission process. Films of non-aligned MWNTs show considerably reduced electron-emission current
densities and larger critical fields.
Received: 25 April 2001 / Accepted: 30 May 2001 / Published online: 25 July 2001 相似文献
11.
I. Savova I. Savatinova P. Kircheva E. Liarokapis 《Applied physics. B, Lasers and optics》2001,73(5-6):565-568
In this work we present polarized Raman measurements of z-cut multimode H:LiNbO3 waveguides in the κi- and βi-phase states. A spectrum with unexpected form and behaviour, originating from the layer at the very surface, was observed
in samples with various degrees of Li–H substitution. Possible reasons for the presence of this strange spectrum are considered.
Received: 16 May 2001 / Revised version: 7 August 2001 / Published online: 23 October 2001 相似文献
12.
A. Lunk P. Bachem P. Scheible L. Ulrich 《Applied Physics A: Materials Science & Processing》2001,72(5):557-564
The development of in situ diagnostics of the most important species and reactions in the plasma and/or on the surface during
thin-film growth is one of the current topics in plasma-enhanced vapor deposition. In situ thin film diagnostic methods which
could be used in plasma processing are restricted due to the presence of electrons and ions. The advantages and disadvantages
of different applicable methods will be discussed. The spectroscopic in situ control of boron nitride film growth is presented
as an example of surface modification in low-temperature, low-pressure plasma processing. The growth of cubic and hexagonal
boron nitride is observed by polarized infrared reflection spectroscopy in absorption and ellipsometric configurations as
well as by single-wavelength ellipsometry in the visible spectral range. Modeling of the experimental results gives detailed
information on growth conditions and internal stress of the films.
Received: 8 August 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001 相似文献
13.
Molar volumes, V, and compactness values, α, of 34 glassy compositions of the GeSeFe system have been obtained using their
measured densities. The property–composition dependences are examined in light of the models proposed for the structure of
these network glasses.
Received: 28 August 2000 / Accepted: 9 January 2001 / Published online: 23 March 2001 相似文献
14.
U. Czarnetzki D. Luggenhölscher H.F. Döbele 《Applied Physics A: Materials Science & Processing》2001,72(5):509-521
Temporally and spatially resolved measurements of the electric field distribution in the sheath region of RF and dc discharges
provide a detailed insight into the sheath and ion dynamics. The electric field is directly related to the sheath ion and
electron densities, the sheath voltage, and the displacement current density. Under certain assumptions also the electron
and ion conduction current densities at the electrode, the ion current density into the sheath from the plasma bulk, the ion
energy distribution function, and the power dissipated in the discharge can be inferred. Furthermore, the electric field distribution
can give an indication of the collision-induced conversion between different ion species in the sheath. Laser spectroscopic
techniques allow the noninvasive in situ measurement of the electric field with high spatial and temporal resolution. These
techniques are based on the spectroscopic measurement of the Stark splitting of Rydberg states of helium and hydrogen atoms.
Two alternative techniques are applied to RF discharges at 13.56 MHz in helium and hydrogen and a pulsed dc discharge in hydrogen.
The measured electric field profiles are analyzed, and the results discussed with respect to the ion densities, currents,
energies, temporal dynamics and species composition.
Received: 26 July 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001 相似文献
15.
Z.-Z. Gu S. Kubo A. Fujishima O. Sato 《Applied Physics A: Materials Science & Processing》2002,74(1):127-129
A dipping method has been developed for the infiltration of nanoparticles into an opal template to fabricate high quality
inverse opal. Titania and silica inverse opal films, with a uniform color over centimeter dimensions were derived. As there
is no need for special substrates or equipment, a widespread application of this method is anticipated.
Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 30 October 2001 相似文献
16.
Development and characterization of Yb-Er laser glass for high average power laser diode pumping 总被引:5,自引:0,他引:5
G. Karlsson F. Laurell J. Tellefsen B. Denker B. Galagan V. Osiko S. Sverchkov 《Applied physics. B, Lasers and optics》2002,75(1):41-46
A new strong erbium laser glass (SELG) based on a boro-alumo-phosphate composition is reported. We discuss the synthesis and
chemical properties together with spectroscopic and thermo-mechanical data. The new glass composition shows excellent laser
performance and withstands high-average power pump radiation. We present laser results at 1.54 μm from flashlamp and laser
pumping. In tests with laser-diode pumped Q-switched Er-Yb microchip lasers, we have achieved up to 150 mW of average output
power and generated 1.2 kW in peak power. Co2+:MgAl2O4 was here used as the saturable absorber.
Received: 21 December 2001 / Revised version: 14 April 2002 / Published online: 8 August 2002 相似文献
17.
T. Glasmacher B.V. Pritychenko P.D. Cottle R.W. Ibbotson K.W. Kemper H. Scheit 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):59-62
Projectile fragmentation provides radioactive beams at intermediate velocities (v/c = 0.3-0.5) by physical means of fragment separation. With the development of position-sensitive photon detectors it has become
possible to measure the energies and directions of photons emitted in-flight from such fast-moving exotic beams. This allows
the reconstruction of the photons' energies emitted from an exotic projectile with high accuracy. It can be advantageous to
employ photon detection in experiments with exotic beams since photons can traverse matter easily and their attenuation can
be calculated. Experiments with standard luminosities can be carried out at intermediate beam energies with thick secondary
targets (order of g/cm2) and very low incident beam rates (order of particle/s or less). Experimental success in this field is strongly correlated
with the development of photon detectors such as position-sensitive scintillation detectors or segmented germanium detectors.
In-beam gamma-ray spectroscopy of fast exotic beams has been successfully used at all projectile fragmentation facilities
in intermediate-energy heavy-ion inelastic scattering experiments, knockout reactions and fragmentation reactions. Here, we
focus on experimental results for neutron-rich exotic nuclei in the π(sd )-shell. Measurements and detector developments carried out at the NSCL at Michigan State University during the last four
years are discussed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
18.
M. Takai W. Jarupoonphol C. Ochiai O. Yavas Y.K. Park 《Applied Physics A: Materials Science & Processing》2003,76(7):1007-1012
Localized physical and chemical reactions induced by focused ion and electron beams, i.e. dual beams, have been used to fabricate
field emitters (FEs) and their arrays, field-emitter arrays (FEAs), without masking and annealing processes. Issues arising
from beam processing such as beam-induced damage and contamination were eliminated to provide FEAs with low leakage current.
Quick prototyping and repairing processes of FEs and FEAs using dual-beam processing have been demonstrated.
Nb- or Au-gated Pt FEAs have been fabricated using dual beams. The fabricated FEAs showed a turn-on voltage of 40 V for field
emission with a typical emission current of about 1 μA/tip.
Received: 21 August 2002 / Accepted: 21 August 2002 / Published online: 12 February 2003
RID="*"
ID="*"Corresponding author. Fax: +81-6/6850-6662, E-mail: takai@rcem.osaka-u.ac.jp 相似文献
19.
A model of deep and shallow traps has been applied in order to explain the temporal development of the signal wave amplification
as well as the pump wave depletion in two-wave-mixing experiments in the crystal Ba0.23Ca0.77TiO3 (BCT). The intensities of the outgoing waves have been studied at different intensities of the incident waves during the
first 500 s before the beams have reached their stable states. On the basis of the obtained temporal dependences of the intensities,
some material parameters of the crystal have been estimated, like excitation cross sections from the deep and shallow traps
(valence levels) into the conduction band, recombination rates from the conduction band into the valence levels, absolute
and redistributed charge densities of the deep and shallow traps, and modulations of the absorption and refractive indices.
Received: 26 May 2000 / Revised version: 26 September 2000 / Published online: 21 February 2001 相似文献
20.
Optical holographic memory using angular-rotationally phase-coded multiplexing in a LiNbO3:Fe crystal 总被引:2,自引:0,他引:2
We propose a new holographic memory scheme based on random-phase-coded multiplexing in a photorefractive LiNbO3:Fe crystal. Experimental results show that rotating a diffuser placed as a random-phase modulator in the path of the reference
beam provides a simple yet effective method of increasing the holographic storage capabilities of the crystal. Combining this
rotational multiplexing with angular multiplexing offers further data-storage possibilities. The advantage of using post-image
versus pre-image phase modulation of the object beam is demonstrated.
Received: 15 August 2000 / Published online: 10 January 2001 相似文献