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1.
A. Lucchesini S. Gozzini 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(2):209-215
By using a diode laser spectrometer based on a commercial heterostructure diode laser operating in free-running mode, line shape parameters of some ammonia ro-vibrational overtones at 790 nm have been measured at room temperature. These
weak absorption lines have been detected by using the wavelength modulation spectroscopy technique with second-harmonic detection.
The broadening and shifting coefficients have been obtained for ten absorption lines by fitting the collected second-harmonic
absorption features and varying the pressure of different buffer gases.
Received 13 February 2002 / Received in final form 18 September 2002 Published online 17 December 2002
RID="a"
ID="a"e-mail: alex@ifam.pi.cnr.it 相似文献
2.
A tunable diode laser (TDL) is used to measure the absorption spectra of the R46 through R54 transitions of the 20012←00001 band of CO2 near 2.0 μm (5000 cm−1) at room temperature and pressures to 10 atm (densities to 9.2 amagat). Spectra are recorded using direct absorption spectroscopy
and wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) in a mixture containing 11% CO2 in air. The direct absorption spectra are influenced by non-Lorentzian effects including finite-duration collisions which
perturb far-wing absorption, and an empirical χ-function correction to the Voigt line shape is shown to greatly reduce error in the spectral model. WMS-2f spectra are shown
to be at least a factor of four less-influenced by non-Lorentzian effects in this region, making this approach more resistant
to errors in the far-wing line shape model and allowing a comparison between the spectral parameters of HITRAN and a new database
which includes pressure-induced shift coefficients. The implications of these measurements on practical, high-pressure CO2 sensor design are discussed. 相似文献
3.
V. R. Galakhov M. Neumann D. G. Kellerman 《Applied Physics A: Materials Science & Processing》2009,94(3):497-500
X-ray absorption, resonant X-ray emission, and X-ray photoelectron spectroscopical methods have been applied for the study
of the electronic structure of defective lithium cobaltites Li
x
CoO2 (0.6≤x≤1.0). Resonant O K
α X-ray emission spectra of LiCoO2 showed localized excitonic states due to a dd transition between occupied and unoccupied Co 3d states. On the base of measurements of Co 3s X-ray photoelectron, Co 2p, and O 1s X-ray absorption spectra, it was established that in defective cobaltites the electronic holes are localized mainly in O
2p states. An evidence of phase separation in Li
x
CoO2 has been found. It was shown that the semiconductor-to-metal transition in Li
x
CoO2 (x<0.76) at about 160 K is not accompanied by changes in the Co 3d electronic configuration which remains 3d
6. 相似文献
4.
A. V. Okotrub L. G. Bulusheva A. G. Kudashov V. V. Belavin D. V. Vyalikh S. L. Molodtsov 《Applied Physics A: Materials Science & Processing》2009,94(3):437-443
Arrays of vertically aligned nitrogen-doped carbon (CN
x
) nanotubes have been synthesized by decomposition of aerosol mixture of acetonitrile and ferrocene at 850°C. Nitrogen concentration
in the outer shells of the CN
x
nanotubes was found from X-ray photoelectron spectroscopy (XPS) data to reach ∼6%. The XPS N 1s spectra and N 1s near-edge X-ray absorption fine structure (NEXAFS) spectra identified three chemical forms of nitrogen in the CN
x
nanotube arrays: pyridine-like, graphitic, and molecular nitrogen. The π
* resonance of molecular nitrogen showed clear polarization dependence that indicates predominant orientation of N2 molecules along the nanotubes axis. The estimated range of the polar angle distribution of the N2 molecules orientation in the CN
x
nanotube array amounts to 15°. 相似文献
5.
L. Ciaffoni B. L. Cummings W. Denzer R. Peverall S. R. Procter G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2008,92(4):627-633
High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different
transitions within the region of the ν
1+ν
2+ν
3 and 2ν
1+ν
2 combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross
sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using
cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H2S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy
(WMS). The set-up sensitivity has been calculated as 1.73×10−8 cm−1 s1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions
has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated
to the intermolecular potentials governing the collision process; the H2S–H2S dimer well depth is estimated to be 7.06±0.09 kJ mol−1. 相似文献
6.
A. Khajehnezhad N. Nikseresht H. Hadipour M. Akhavan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):461-467
We have compared the electrical and magnetic properties of Ru(Gd1.5−x
Pr
x
)Ce0.5Sr2Cu2O10−δ
(Pr/Gd samples) with x = 0.0, 0.01, 0.03, 0.033, 0.035, 0.04, 0.05, 0.06, 0.1 and RuGd1.5(Ce0.5−x
Pr
x
) Sr2 Cu2O10−δ
(Pr/Ce samples) with x = 0.0, 0.01, 0.03, 0.05, 0.08, 0.1, 0.15, 0.2 prepared by the standard solid-state reaction technique. We obtained the XRD
patterns for different samples with various x. The lattice parameters versus x for different substitutions have been obtained from Rietveld analysis. To determine how the magnetic and superconducting
properties of these layered cuprate systems can be affected by Pr substitution, the resistivity, and magnetoresistivity, with
H
ext
varying from 0.0 to 15 kOe, have been measured at various temperatures. Superconducting transition temperature T
c
and magnetic transition T
irr
, have been obtained through resistivity and ac susceptibility measurements. The T
c
suppression due to Pr/Gd and Pr/Ce substitutions show competition between pair breaking by magnetic impurities, hole doping
due to different valances of ions, difference in ionic radii, and oxygen stoichiometry. Pr/Gd substitution suppresses superconductivity
more rapidly than for Pr/Ce, showing that the effect of hole doping and magnetic impurity pair breaking is stronger than the
difference in ionic radii. In Pr/Gd substitution, the small difference between the ionic radii of Pr3+,4+ and Gd3+, and absorption of more oxygen due to the higher valence of Pr with respect to Gd, decreases the mean Ru-Ru distance, and
as a result, the magnetic exchange interaction becomes stronger with the increase of x. However, Pr/Ce substitution has the opposite effect. The magnetic parameters such as H
c
, obtained through magnetization measurements versus applied magnetic field isotherm at 77 K and room temperatures, become
stronger with x in Pr/Gd and weaker with x in Pr/Ce substitution. 相似文献
7.
A sensor based on quartz-enhanced photoacoustic spectroscopy (QEPAS) was evaluated for the detection of trace levels of ethylene
at atmospheric pressure using a fiber coupled DFB diode laser emitting in the 1.62 μm spectral range. A noise-equivalent QEPAS signal of ∼4 ppm C2H4 was achieved for a 0.7 s data acquisition time using wavelength-modulation with a second-harmonic detection scheme on the
strongest C2H4 absorption peak at 6177.14 cm−1 with an average optical power of ∼15 mW. Improved detection sensitivity of 0.5 and 0.3 ppm C2H4 (1σ) was demonstrated using longer averaging time of 70 and 700 s, respectively. Important characteristics for the QEPAS based
sensor operation in real-world conditions are presented, particularly the influence of external temperature variations. Furthermore,
the response time of the ethylene sensor was measured in different configurations and it is shown that the QEPAS technique
can provide a response time in a few seconds range even without active gas flow. 相似文献
8.
Lead-free (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics have been prepared by an ordinary sintering technique and their structure, ferroelectric and piezoelectric properties
have been studied. The results of X-ray diffraction show that La2+ and Ba2+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a new solid solution with a pure perovskite structure, and a morphotropic phase boundary (MPB) exists at
0.04<x<0.10. Compared with pure Bi0.5Na0.5TiO3 ceramics, the (Bi0.98−x
La0.02Na1−x
)0.5Ba
x
TiO3 ceramics possess much smaller coercive field E
c and larger remanent polarization P
r. Because of the low E
c (3.38 kV/mm), large P
r (46.2 μC/cm2) and the formation of the MPB of rhombohedral and tetragonal phases, the piezoelectric properties of the ceramics are significantly
enhanced at x=0.06: d
33=181 pC/N and k
p=36.3%. The depolarization temperature T
d reaches a minimum value near the MPB. The ceramics exhibit relaxor characteristic, which is probably a result from the cation
disordering in the 12-fold coordination sites. The temperature dependences of the ferroelectric and dielectric properties
suggest that the ceramics may contain both polar and non-polar regions at the temperatures above T
d. 相似文献
9.
A. H. Moudden 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):173-183
Several structures for off-stoichiometric beryllium diboride dicarbide Be1−xB2C2 have been designed, and their properties studied from first-principles density functional methods. Among the most stable
phases examined, the layered hexagonal structures are shown to exhibit various features in the electronic properties and in
the lattice dynamics reminiscent of the superconducting magnesium diboride and alkaline earth-intercalated graphites. For
substoichiometric composition x ∼ 1/3, the system is found metallic with a moderately strong electron-phonon coupling through a predominant contribution
arising from high frequency streching modes modulating the σ-bonding of the B-C network, and a weaker contribution at medium frequency range of the phonon spectra, arising from the intercalent
motion coupled to the π-bonding states. Further, anharmonicities emerging from the proximity of the Fermi level to the σ-band edge, contributes to reduce the phonon softening hence stabilizing the structure. All these effects appear to combine
favourably to produce a high temperature phonon-superconductivity. 相似文献
10.
A series of stoichiometric and nonstoichiometric copper–chalcogenide nanocrystallines with different morphologies, e.g., extremely
high aspect ratio nanofibers (Cu9S8), tubular structure (Cu
x
S (x=∼1.86–1.96), nanorods (CuS, Cu31S16), platelets (β-CuSe, Cu3Se2), rope-like Cu3Se2, as well as spherical nanoparticles (Cu7Se4, Cu2−x
Se), have been successfully synthesized in 20 vol% water and 80 vol% organic solvents mixture under mild conditions. The products
were characterized by various techniques, including X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), electronic diffraction (ED), and high-resolution transmission electron microscopy (HRTEM). The
studies of the optical properties revealed that the copper chalcogenides have a wide absorption in the range of about 400–700 nm,
with accessional IR band. Systematic studies showed that the mixture of 20 vol% water and 80 vol% organic solvents played
a key role in controlling the copper chalcogenides with different morphologies and phases. 相似文献
11.
Pramod Bhatt E. Carlegrim A. Kanciurzewska M. P. de Jong M. Fahlman 《Applied Physics A: Materials Science & Processing》2009,95(1):131-138
Thin film iron-tetracyanoethylene Fe(TCNE)
x
, x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed
physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron
spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE)
x
is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results.
The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge
transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE)
x
system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T
C
) seen for Fe(TCNE)
x
-type magnets. 相似文献
12.
D. E. Appelbe R. A. E. Austin G. C. Ball J. A. Cameron B. Djerroud T. E. Drake S. Flibotte C. D. O’Leary A. Melarangi C. E. Svensson J. C. Waddington D. Ward 《The European Physical Journal A - Hadrons and Nuclei》2000,8(2):153-155
The decays of 2557Mn32 and 2558Mn33 have been studied with the 8π Spectrometer following the reaction 48Ca(13C,pxn)60 − x
Mn at a beam energy of 40 MeV. The level schemes of these two nuclei have been extended, and the multipolarities of the observed
transitions have been determined. 相似文献
13.
V. N. Ishchenko V. N. Lisitsyn A. M. Razhev 《Applied Physics A: Materials Science & Processing》1977,13(1):55-58
NdxLa1−xP5O14 (0.25≦x≦1) single crystals, placed within a confocal optical resonator, were pumped with ruby laser fundamental and second-harmonic
nanosecond pulses. In both cases laser oscillations at 1.05 μm exceeding in duration many times the pumping pulse were obtained. 相似文献
14.
Ning Tang Bo Shen Kui Han Xiao-Wei He Chun-Ming Yin Zhi-Jian Yang Zhi-Xin Qin Guo-Yi Zhang Tie Lin Wen-Zheng Zhou Li-Yan Shang Jun-Hao Chu 《Applied Physics A: Materials Science & Processing》2009,96(4):953-957
The subband structure and occupation in the triangular quantum well at Al
x
Ga1−x
N/GaN heterointerfaces have been investigated by means of temperature dependent Shubnikov–de Haas (SdH) measurements at low
temperatures and high magnetic fields under illumination. After the illumination of the heterostructures, the total two-dimensional
electron gas concentration increases, and the SdH oscillation amplitudes are enhanced when there is no additional subband
occupation. It is also found that the energy separation between the subbands decreases after the illumination. We suggest
that the illumination decreases the electric field and thus weakens the quantum confinement of the triangular quantum well
at Al
x
Ga1−x
N/GaN heterointerfaces. The GaN layer is thought to be the primary contributor of the excited electrons by the illumination. 相似文献
15.
In this paper, we report on the pulsed laser deposition of epitaxial (0002) oriented Zn1−x
Mg
x
O thin films onto (0001) sapphire substrate in O2 ambient at different deposition temperatures. Pulsed laser deposited Zn1−x
Mg
x
O films showed (0002) oriented hexagonal wurtzite structure up to 34% of Mg concentration. The bandgap of Zn1−x
Mg
x
O thin films is successfully tuned from 3.3 to 4.2 eV by adjusting the Mg concentration x=0.0 to x=0.34. Pulsed laser deposited Zn1−x
Mg
x
O thin films were characterized by XRD, AFM, SEM, PL and UV–VIS spectrometer. We have also studied the effect of deposition
temperature on to the structure, surface morphology and optical properties of Zn1−x
Mg
x
O thin films. 相似文献
16.
Tunable diode-laser absorption of CO2 near 2.7 μm incorporating wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) is used to provide a
new sensor for sensitive and accurate measurement of the temperature behind reflected shock waves in a shock-tube. The temperature
is inferred from the ratio of 2f signals for two selected absorption transitions, at 3633.08 and 3645.56 cm−1, belonging to the ν
1+ν
3 combination vibrational band of CO2 near 2.7 μm. The modulation depths of 0.078 and 0.063 cm−1 are optimized for the target conditions of the shock-heated gases (P∼1–2 atm, T∼800–1600 K). The sensor is designed to achieve a high sensitivity to the temperature and a low sensitivity to cold boundary-layer
effects and any changes in gas pressure or composition. The fixed-wavelength WMS-2f sensor is tested for temperature and CO2 concentration measurements in a heated static cell (600–1200 K) and in non-reactive shock-tube experiments (900–1700 K) using
CO2–Ar mixtures. The relatively large CO2 absorption strength near 2.7 μm and the use of a WMS-2f strategy minimizes noise and enables measurements with lower concentration,
higher accuracy, better sensitivity and improved signal-to-noise ratio (SNR) relative to earlier work, using transitions in
the 1.5 and 2.0 μm CO2 combination bands. The standard deviation of the measured temperature histories behind reflected shock waves is less than 0.5%.
The temperature sensor is also demonstrated in reactive shock-tube experiments of n-heptane oxidation. Seeding of relatively
inert CO2 in the initial fuel-oxidizer mixture is utilized to enable measurements of the pre-ignition temperature profiles. To our
knowledge, this work represents the first application of wavelength modulation spectroscopy to this new class of diode lasers
near 2.7 μm. 相似文献
17.
M. Ahmad P. Kumar N. Suri J. Kumar R. Thangaraj 《Applied Physics A: Materials Science & Processing》2009,94(4):933-937
The crystallization kinetics of Sn10Sb20−x
Bi
x
Se70 (x=0,2,4,6,8) chalcogenide system has been studied. Crystallization studies using differential scanning calorimetry under nonisothermal
conditions with different heating rates are reported. The glass transition temperature is found to increase with the increase
in heating rate as well as with the addition of bismuth. The apparent activation energy for glass transition and that for
crystallization have been determined using the Kissinger equation. Thermal stability and glass forming tendency have also
been studied. 相似文献
18.
L. Chkhaidze T. Djobava L. Kharkhelauri M. Mosidze 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):299-306
A detailed study of pion production in central Mg-Mg collisions at a momentum of 4.3 GeV/c per incident nucleon was carried
out with use of the setup GIBS. The average kinematical characteristics of pions (multiplicity n
−, momentum P, transverse momentum P
T, emission angle Θ, rapidity Y) and corresponding distributions have been obtained. The experimental results have been compared with the predictions of
the Quark Gluon String Model (QGSM) and satisfactory agreement between the experimental data and the model has been found.
The QGSM reproduces also the dependence of average P
T on n
−.
The temperatures of π− mesons have been estimated in the rapidity interval of 0.5 ≤ Y ≤ 2.1. A satisfactory fit for π− mesons has been achieved by using a form involving two temperatures T
1 and T
2. It is found that the QGSM underestimates T
2 by (10−15)%.
The data have been analyzed using the transverse momentum technique. The observed dependence of the <P
x
′(Y)> on Y shows the S-shape behaviour. The slope at midrapidity F has been determined. The QGSM reproduces the <P
x> distribution satisfactorily, but underestimates the parameter F.
Received: 2 August 1997 / Revised version: 17 November 1997 相似文献
19.
Dunmin Lin Qiaoji Zheng Chenggang Xu K. W. Kwok 《Applied Physics A: Materials Science & Processing》2008,93(2):549-558
(1−x−y)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3– yBi0.5Li0.5TiO3 lead-free piezoelectric ceramics have been prepared by an ordinary sintering technique, and their structure, electrical properties,
and temperature characteristics have been studied systematically. The ceramics can be well-sintered at 1050–1150 °C. The increase
in K+ concentration decreases the grain-growth rate and promotes the formation of grains with a cubic shape, while the addition
of Li+ decreases greatly the sintering temperature and assists in the densification of BNT-based ceramics. The results of XRD diffraction
show that K+ and Li+ diffuse into the Bi0.5Na0.5TiO3 lattices to form a solid solution with a pure perovskite structure. As x increases from 0.05 to 0.50, the ceramics transform gradually from rhombohedral phase to tetragonal phase and consequently
a morphotropic phase boundary (MPB) is formed at 0.15≤x≤0.25. The concentration y of Li+ has no obvious influence on the crystal structure of the ceramics. Compared with pure Bi0.5Na0.5TiO3, the partial substitution of K+ and Li+ for Na+ lowers greatly the coercive field E
c and increases the remanent polarization P
r of the ceramics. Because of the MPB, lower E
c and large P
r, the piezoelectricity of the ceramics is improved significantly. For the ceramics with the compositions near the MPB (x=0.15–0.25 and y=0.05–0.10), the piezoelectric properties become optimum: piezoelectric coefficient d
33=147–231 pC/N and planar electromechanical coupling factor k
P=20.2–41.0%. In addition, the ceramics exhibit relaxor characteristic, which probably results from the cation disordering
in the 12-fold coordination sites. The depolarization temperature T
d shows a strong dependence on the concentration x of K+ and reaches the lowest values at the MPB. The temperature dependences of the ferroelectric and dielectric properties at high
temperatures may imply that the ceramics may contain both the polar and non-polar regions at temperatures above T
d. 相似文献
20.
W H Madhusudan Sheelavathi Kollali P R Sarode M S Hegde P Ganguly C N R Rao 《Pramana》1979,12(4):317-329
X-ray and ultraviolet photoelectron spectroscopy as well as x-ray absorption spectroscopy have been employed to investigate
transition metal oxide perovskites of the general formula ABO3 (A = La or rare-earth ion, B=trivalent transition metal ion). Systematics in the core levels and in the valence bands in
the series of LaBO3 compounds have been discussed. Lanthanum chemical shifts in the x-ray absorption spectra in this series show interesting
trends. Photoelectron spectra of the solid solutions, LaNi1−x
Co
x
O3, LaNi1−x
Fe
x
O3 and LaFe1−x
Co
x
O3 show that the rigid band model is applicable to these systems. It is shown that x-ray photoelectron spectroscopy can be employed
to identify multiple oxidation states of transition metal ions in oxide perovskites.
Communication No. 30 from the Solid State and Structural Chemistry Unit.
An erratum to this article is available at . 相似文献