共查询到20条相似文献,搜索用时 46 毫秒
1.
J. Hoffman W. Mróz A. Prokopiuk Z. Szymanski 《Applied Physics A: Materials Science & Processing》2008,92(4):921-926
The plasma plume induced during ArF laser ablation of a graphite target is studied. Velocities of the plasma expansion front
are determined by the optical time of flight method. Mass center velocities of the emitting atoms and ions are constant and
amount to 1.7×104 and 3.8×104 m s−1, respectively. Higher velocities of ions result probably from their acceleration in electrostatic field created by electron
emission prior to ion emission. The emission spectroscopy of the plasma plume is used to determine the electron densities
and temperatures at various distances from the target. The electron density is determined from the Stark broadening of the
Ca II and Ca I lines. It reaches a maximum of ∼9.5×1023 m−3 30 ns from the beginning of the laser pulse at the distance of 1.2 mm from the target and next decreases to ∼1.2×1022 m−3 at the distance of 7.6 mm from the target. The electron temperature is determined from the ratio of intensities of ionic
and atomic lines. Close to the target the electron temperature of ∼30 kK is found but it decreases quickly to 11.5 kK 4 mm
from the target. 相似文献
2.
Laser-induced fluorescence study of a xenon Hall thruster 总被引:1,自引:0,他引:1
R.J. Cedolin W.A. Hargus Jr. P.V. Storm R.K. Hanson M.A. Cappelli 《Applied physics. B, Lasers and optics》1997,65(4-5):459-469
2
0→6p[3/2]2(3P2-1D2) transition at 823.2 nm and the xenon-ion 5d[3]7/2→6p[2]5/2
0(4D7/2-4P5/2) transition is used to measure plasma parameters in the plume of a laboratory-model xenon Hall thruster. The Hall discharge
operates nominally at 62 V, 4.2 A, and 3.2 mg s-1 xenon flow, with an overall thruster power of 320 W. A tunable semiconductor diode laser and an Ar+-pumped dye laser are used to probe the respective excited-state transitions. Axial velocity measurements are made at a number
of axial and radial locations up to 4.5 cm downstream of the thruster-exit plane and under a variety of thruster operating
conditions. Neutral velocities from 100 m s-1 to 400 m s-1 and ion velocities as high as 12 km s-1 are calculated from measured Doppler shifts. The charge-exchange phenomenon evidently does not significantly affect the xenon
neutrals. The spectral-line shapes of the ion indicate a spread in ion energies through a non-Maxwellian distribution of axial
velocities. Neutral kinetic temperatures of 500 (±200) K are observed under standard operating conditions. Zeeman and Stark
effects on the spectral-line shapes, from the thruster’s magnetic and electric fields, are not substantial. The measured line
center of the ion transition is 16521.23 (±0.02) cm-1.
Received: 20 January 1997/Revised version: 12 May 1997 相似文献
3.
Kun Yin Hui Xu Gaoyu Zhong Gang Ni Wei Huang 《Applied Physics A: Materials Science & Processing》2009,95(2):595-600
A novel europium complex Eu(TTA)3(CPPO)2 (1) (TTA=thenoyltrifluoroacetone, CPPO=9-[4-(diphenyl-phosphinoyl)-phenyl]-9H-carbazole) based on the phosphine oxide ligand
with bipolar structure was used to fabricate double-layer devices. The strong hole injection and transport ability of 1 was proved. The luminance of 414 cd m−2 was achieved with the device configuration ITO/Eu(TTA)3(CPPO)2(40 nm)/BCP (30 nm)/Mg:Ag (BCP = 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline), which is favorable among double-layer
organic light emitting devices based on small molecular Eu3+ complexes. The maximum current efficiency of 2.44 cd A−1 and external quantum efficiency of 1.55% demonstrate the potential application of 1 as a promising candidate for high-efficiency, simple-structure and pure red-emitting devices. 相似文献
4.
R.?Wilfinger J.?Lettry the EURISOL?Task Workgroup 《The European physical journal. Special topics》2007,150(1):379-382
EURISOL foil-targets have to withstand a primary proton
beam of 1 GeV kinetic energy and up to 100 μA
beam current. These foil targets will be based on previous
high-power target concepts, i.e. the RIST target [J.R.J. Bennett et al.,
Nucl. Instrum. Meth. Phys. Res. B 126, 117 (1997)]
or high power targets used at
TRIUMF [P. Bricault et al.,
Nucl. Instrum. Meth. Phys. Res. B 204, 319 (2003), M. Dombsky et al.,
Nucl. Instrum. Meth. Phys. Res. B 204, 191 (2003)].
A single target unit is capable of dissipating up to 25 kW,
hence, several target units can be merged together by individual
transfer lines to one common ion source. The single target units
will be irradiated by a proton beam in a time sharing mode to
distribute the primary proton beam current to the individual
target units. In this feasibility study the necessary properties
of high-power foil targets are discussed and the requirements to
design a foil target according to the proton beam parameters
[CITE] for the future EURISOL facility
are given. 相似文献
5.
Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine
(L1), 1,10-phenanthroline (L2), hydroxyproline (L3) and 2,6-pyridine dicarboxylic acid (L4) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility
measurements. The complexes [CuLL1](NO3)2 [1], [CuLL2](NO3)2 [2], [CuLL3](NO3) [3] and [CuLL4] (NO3) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes.
The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy,
thermal melting and viscosity measurements .The binding constant (Kb) of the above four metal complexes were determined as 5.43 × 104 M,−1 2.56 × 104 M−1, 1.21 × 104 M−1 and 1.57 × 104 M−1 respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex
1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through
groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows
that 1, 2 and 3 complexes cleave DNA through redox chemistry. 相似文献
6.
Yata PK Shilpa M Nagababu P Reddy MR Kotha LR Gabra NM Satyanarayana S 《Journal of fluorescence》2012,22(3):835-847
The three Ru(II) complexes of [Ru(phen)2dppca]2+ (1) [Ru(bpy)2dppca]2+ (2) and [Ru(dmb)2dppca]2+ (3) (where phen = 1,10 phenanthroline, bpy = 2,2-bipyridine, dmb = 2 ,2-dimethyl 2′,2′-bipyridine and polypyridyl ligand
containing a single carboxylate functionality dppca ligand (dipyridophenazine-11-carboxylic acid) have been synthesized and
characterized. These complexes have been shown to act as promising calf thymus DNA intercalators and a new class of DNA light
switches, as evidenced by UV-visible and luminescence titrations with Co2+ and EDTA, steady-state emission quenching by [Fe(CN)6]4− and KI, DNA competitive binding with ethidium bromide, viscosity measurements, and DNA melting experiments. The results suggest
that 1, 2, and 3 complexes bind to CT-DNA through intercalation and follows the order 1 > 2 > 3. Under irradiation at 365 nm,
the three complexes have also been found to promote the photocleavage of plasmid pBR322 DNA. 相似文献
7.
By using noninteger n-Slater type orbitals in combined Hartree–Fock–Roothaan method, self-consistent field calculations of
orbital and lowest states energies have been performed for the isoelectronic series of open shell systems K[Ar]4s
03d
1 (2
D) (Z = 19–30) and Cr + [Ar]4s
03d
5 (6
S) (Z = 24–30). The results of the calculations for the orbital and total energies obtained by using minimal basis-sets of noninteger
n-Slater type orbitals are given in the tables. The results are compared with the extended-basis Hartree–Fock computations.
The orbital and total energies are in good agreement with those presented in the literature. The results can be useful in
the study of various properties of heavy atomic systems when the combined Hartree–Fock–Roothaan approach is employed. 相似文献
8.
A complex Fe(phen)2·PHPIP·3ClO4·2H2O, where phen = 1,10-phenanthroline and PHPIP = p-hydroxyphenylimidazo[f]1,10-phenanthroline, was synthesized and acted as a good fluorescence indicator based on its interaction
with double-duplex DNA. Then a fiber-optic DNA biosensor of fluorimetric detection was developed based on the recognition
of target DNA in DNA hybridization assays. A probe ssDNA was covalently immobilized onto the surface of quartz optical fibers
and then the probe ssDNA hybridized with complementary ssDNA introduced into the local environment of the sensor. The hybridization
with complementary strands was monitored in real time by fluorimetric detection. Several factors affecting the probe immobilization,
target DNA hybridization, and indicator binding reactions were optimized to maximize the sensitivity and shorten the assay
time. Using this method, a sequence of the 16-mer oligonucleotides could be quantified over the range from 4.98 × 10−7 to 4.88 × 10−6 M and a detection limit of 1.08 × 10−7 M. And the designed optic-fiber biosensor could be conveniently regenerated by thermal denature. The utility of the novel
hybridization indicator could provide a simple, rapid, low toxicity and reusable detection. 相似文献
9.
6-Hydroxy chromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb]
have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, 1H NMR, thermogravimety/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula
of the complex is [Ln L·(NO3)2]·NO3. Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex
bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA
was 2.48 × 105 M−1 through fluorescence titration data. 相似文献
10.
We present measurements of the net-induced gain on the 5d–4f transition at 186 nm in LiYF4 : Nd3+ optically pumped by radiation from a molecular fluorine laser. It is found that for LiYF4 : Nd3+, one of a series of potential continuously tunable VUV lasers, relatively strong excited-state absorption results in net-induced
loss. The prospects for VUV laser operation being realised in other rare-earth-doped fluorides is discussed.
Received: 4 March 1996/Revised version: 10 July 1996 相似文献
11.
In the present work, five systems of samples have been prepared by the solution casting technique. These are the plasticized
poly(methyl methacrylate) (PMMA-EC) system, the LiCF3SO3 salted-poly(methyl methacrylate) (PMMA-LiCF3SO3) system, the LiBF4 salted-poly(methyl methacrylate) (PMMA-LiBF4) system, the LiCF3SO3 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiCF3SO3) system, and the LiBF4 salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiBF4) system. The conductivities of the films from each system are characterized by impedance spectroscopy. The room temperature
conductivity in the pure PMMA sample and (PMMA-EC) system is 8.57 × 10−13 and 2.71 × 10−11 S cm−1, respectively. The room conductivity for the highest conducting sample in the (PMMA-LiCF3SO3), (PMMA-LiBF4), ([PMMA-EC]-LiCF3SO3), and ([PMMA-EC]-LiBF4) systems is 3.97 × 10−6, 3.66 × 10−7, 3.40 × 10−5, and 4.07 × 10−7 S cm−1, respectively. The increase in conductivity is due to the increase in number of mobile ions, and decrease in conductivity
is attributed to ion association. The increase and decrease in the number of ions can be implied from the dielectric constant,
ɛr-frequency plots. The conductivity–temperature studies are carried out in the temperature range between 303 and 373 K. The
results show that the conductivity is increased when the temperature is increased and obeys Arrhenius rule. The plots of loss
tangent against temperature at a fixed frequency have showed a peak at 333 K for the ([PMMA-EC]-LiBF4) system and a peak at 363 K for the ([PMM-EC]-LiCF3SO3) system. This peak could be attributed to β-relaxation, as the measurements were not carried out up to glass transition temperature,
T
g. It may be inferred that the plasticizer EC has dissociated more LiCF3SO3 than LiBF4 and shifted the loss tangent peak to a higher temperature.
Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006 相似文献
12.
Three new pyridylindolizine derivatives, 1, 2, 3-tricarbometoxi-7-(4-pyridyl)-pyrrolo[1, 2-a]pyridine (I), 1,2-dicarboethoxy-3-(4-bromobenzoyl)-7-(4-pyridyl)-pyrrolo[1,2-a]pyridine (II) and its isomer 1,2-dicarboethoxy-3- (4-bromobenzoyl) -5- (2-pyridyl) -pyrrolo[1, 2-a]pyridine (III) have been investigated in different solutions by UV-VIS absorption, steady-state, and time-resolved fluorescence methods. The effects of the substituent and solvent on the spectroscopic properties have been demonstrated. The fluorescence decay data could be fitted to a single-exponential function. The lifetime values are higher in protic polar than in aprotic apolar solvents for compound I. In the case of compounds II and III the fluorescence intensities and lifetimes are very low, with the exception of III in aprotic solvents. The absorption and fluorescence properties of the compounds showed a solvent dependence. 相似文献
13.
Absolute frequency and isotope shift measurements of the cooling transition in singly ionized indium
Y. H. Wang R. Dumke J. Zhang T. Liu A. Stejskal Y. N. Zhao Z. H. Lu L. J. Wang Th. Becker H. Walther 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(2):307-311
We report greater than two orders of magnitude improvements in the absolute frequency and isotope shift measurements of the
In+ 5s2
1S0 (F = 9/2)–5s5p 3P1 (F = 11/2) transition near 230.6 nm. The laser-induced fluorescence from a single In+ in a radio-frequency trap is detected. The fourth-harmonic of a semiconductor laser is used as the light source. The absolute
frequency is measured with the help of a frequency comb referenced to a Cs atomic clock. The resulting transition frequencies
for isotopes 115In+ and 113In+ are measured to be 1 299 648 954.54(10) MHz and 1 299 649 585.36(16) MHz, respectively. The deduced cooling transition frequency
difference is 630.82(19) MHz. By taking into account of the hyperfine interaction, the isotope shift is calculated to be 695.76(1.68) MHz. 相似文献
14.
X. Baillard M. Fouché R. Le Targat P. G. Westergaard A. Lecallier F. Chapelet M. Abgrall G. D. Rovera P. Laurent P. Rosenbusch S. Bize G. Santarelli A. Clairon P. Lemonde G. Grosche B. Lipphardt H. Schnatz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(1):11-17
We present a new evaluation of an 87Sr optical lattice clock using spin polarized atoms. The frequency of the
1S0→3P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional uncertainty of
2.6×10-15, a value that is comparable to the frequency difference between the various primary standards throughout the
world. This measurement is in excellent agreement with a previous one of similar accuracy [Phys. Rev. Lett. 98, 083002 (2007)]. 相似文献
15.
P. Podio-Guidugli 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(3):417-424
Within the framework of a dynamic version of micromagnetics [1,2], the space-time evolution of magnetization in a rigid, saturated ferromagnet is governed by the following equation: γ-1
= ×( + + div
), where the interaction couple × and the couple stress are to be constitutively specified. Under constitutive assumptions for , , and the free energy ψ, that allow for equilibrium response and viscosity out of equilibrium and agree with the dissipation
principle -
.
+
. ∇ - ≥ 0, the above evolution equation yields a broad generalization of the standard Gilbert equation. In particular, while the
standard Gilbert equation only incorporates relativistic dissipation, it is shown that the dissipation mechanisms compatible
with the generalized Gilbert equation include exchange dissipation [2], dry-friction dissipation [3], and others. It is also
shown that the additional term proposed in [4] to account for exchange dissipation, rather than having a genuine dissipative
nature, modifies instead the nature of possible equilibria; and that such a modification is an automatic side effect when
dry-friction dissipation is incorporated in the manner of [3].
Received 31 October 2000 相似文献
16.
N. A. Nemkovich H. Detert V. Schmitt Yu. V. Kruchenok 《Journal of Applied Spectroscopy》2012,79(3):353-359
Absorption and fluorescence spectra of octupolar centrosymmetric oligophenylenevinylene dyes (E,E)-bis[2-(4-hexyloxyphenyl)ethenyl]-(E,E)-3,6-bis-[2-(4-N,N-dipropylaminophenyl)ethenyl]pyrazine and (E,E,E,E)-2,3,5,6- tetra-[2-(4-hexyloxyphenyl)ethenyl]pyrazine were measured in various solvents. An electro-optical absorption method was used to determine their dipole moments as μ g = 6.1∙10–30 and 3.4∙10–30 C∙m in the equilibrium ground state and the increased values ∆ a μ = 11.9∙10–30 and 8.2∙10–30 C∙m upon excitation into a Franck–Condon state. Quantum-chemical calculations showed that the molecules had non-planar configurations. The π,π-conjugated system was localized on the most planar part of the molecule that was responsible for light absorption in the range 300–450 nm due to a change in the geometry of the molecules in the ground state. Localized excitation of the molecules caused their dipole moments ∆ a μ to change significantly. 相似文献
17.
This paper reports the synthesis of high upconversion luminescent Gd2O3: Er3+, Yb3+ nanophosphor through optimized combustion route using urea as a reducing agent. The paper also reports the first observation
of upconversion emission bands extending upto the UV region (335, 366 and 380 nm) in Er3+–Yb3+ co-doped phosphor materials. The fuel to oxidizer ratio has been varied to obtain the maximum upconversion luminescence.
Three high intensity bands are found at 408, 523–548 and 667 nm due to the 4G11/2 → 4I15/2, 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively, along with the other bands. Input excitation power dependence has been studied for different transitions,
and the saturation effect and decrease in the slope of different transitions at higher input pump power has been explained.
Heat treatments of the samples show change in crystallite phase/size and relative upconversion luminescence intensities of
blue, green and red bands. The color of the phosphor emission has shown to be tunable with change in the crystal structure
as well as on excitation laser power and Er3+–Yb3+ concentration. The property of color tunability of the phosphor material has been used to record the fingerprint in different
colors. Also, the future prospect of the nanocrystalline phosphor material as a sensor for temperature, using FIR method,
has been explored. 相似文献
18.
Efficient room-temperature operation of 4
F
3/24
I
9/2 transitions in diode-end-pumped Nd:YAG lasers at 946 nm and 938.5 nm is reported. 7.0-W continuous-wave output power at 946 nm
and 3.9 W at 938.5 nm have been obtained. An analytical model has been developed for the quasi-three-level laser including
the influence of energy-transfer upconversion. Frequency doubling of these transitions in periodically poled KTP generated
blue light at 473 nm and 469 nm. Both single-pass extra-cavity as well as intracavity schemes have been investigated.
Received: 31 July 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +46-8/750-5430, E-mail: stefan.bjurshagen@acreo.se 相似文献
19.
T. Gasmi H.A. Zeaiter G. Ropero A. González Urena 《Applied physics. B, Lasers and optics》2000,71(2):169-175
This paper presents the construction, use and characterisation of a laser-induced sealed plasma shutter to clip off the nitrogen
pulse tail of a CO2-TEA laser-based lidar dial system. Investigation of the optimum gas filling pressure, temporal profile of the clipped pulse,
and the laser threshold power intensities to achieve ionisation growth and breakdown in helium, argon, and nitrogen are also
presented. Values of these power density thresholds lie between 3×1011 W cm-2–5×1012 W cm-2, 2×1011 W cm-2–2×1012 W cm-2 and 3×1013 W cm-2–2×1014 W cm-2 for helium, argon, and nitrogen, respectively. The range resolution attainable with the present clipped pulses is 15 m, which
is 30 times better than that readily obtained with the nitrogen-tailed pulses. Field measurements of the lidar returns with
the clipped pulse from a co-operative target are presented.
Received: 27 December 1999 / Revised version: 11 February 2000 / Published online: 27 April 2000 相似文献
20.
So Yeon Bang Kyung Ju Lee Joo Hwan Koh Moon-Sung Kang Yong Soo Kang Jong Hak Kim 《Ionics》2008,14(2):143-148
In this paper, we aim to prepare polymer electrolytes consisting of NaI and I2 dissolved in poly(ethylene oxide) (PEO) and dioctyl phthalate (DOP) as an additive and apply the electrolytes to dye-sensitized
solar cells (DSSC). Upon the incorporation of salt, the phthalic-stretching C=O bands of DOP in Fourier transform infrared
spectra shifted to a lower wave number (Δf = 93 cm−1), confirming the unusual strong complex formation between sodium ions and phthalic oxygen. Coordinative interactions and
structural changes of PEO/NaI/I2/DOP electrolytes have also been characterized by wide angle X-ray scattering, presenting an almost amorphous structure of
the polymer electrolytes. The ionic conductivity of the polymer electrolytes reached ∼10–4 S/cm at room temperature at the mole ratio of [EO]:[Na]:[DOP] = 10:1:0.5, as determined by the four-probe method. DSSC using
the polymer electrolytes and conductive indium tin oxide glasses exhibited 2.9% of overall energy conversion efficiency (=P
max/P
in × 100) at one sun condition (100 mW/cm2). The good interfacial contact between the electrolytes and the dye-attached nanocrystalline TiO2 layers were verified by field-emission scanning electron microscopy. 相似文献