共查询到20条相似文献,搜索用时 593 毫秒
1.
High-resolution electron microscopy of individual metallofullerene molecules on the dipole orientations in peapods 总被引:1,自引:0,他引:1
K. Suenaga T. Okazaki K. Hirahara S. Bandow H. Kato A. Taninaka H. Shinohara S. Iijima 《Applied Physics A: Materials Science & Processing》2003,76(4):445-447
Electron microscopy with atomic sensitivity enables us to obtain a direct image of the intra-molecular structure of metallofullerenes
encapsulated inside single-walled carbon nanotubes. By a comparison of high-resolution images with a simulation to extract
the relative atom positions for encaged metal atoms in each molecule, the distribution of the molecular orientations and interactions
between adjacent molecules in metallofullerene peapods have been statistically analyzed. The results are suggestive of strong
interactions between fullerene–fullerene and fullerene–tube in peapods at room temperature.
Received: 10 October 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/61-6310, E-mail: suenaga-kazu@aist.go.jp 相似文献
2.
T. Lippert M. Hauer C.R. Phipps A. Wokaun 《Applied Physics A: Materials Science & Processing》2003,77(2):259-264
The ablation characteristics of various polymers were studied at low and high fluences for an irradiation wavelength of 308 nm.
The polymers can be divided into three groups, i.e. polymers containing triazene groups, designed ester groups, and reference
polymers, such as polyimide. The polymers containing the photochemically most active group (triazene) exhibit the lowest thresholds
of ablation (as low as 25 mJ cm-2) and the highest etch rates (e.g. 250 nm/pulse at 100 mJ cm-2), followed by the designed polyesters and then polyimide. Neither the linear nor the effective absorption coefficients have
a clear influence on the ablation characteristics. The different behavior of polyimide might be explained by a pronounced
thermal part in the ablation mechanism. The laser-induced decomposition of the designed polymers was studied by nanosecond
interferometry and shadowgraphy. The etching of the triazene polymer starts and ends with the laser pulse, indicating photochemical
ablation. Shadowgraphy reveals mainly gaseous products and a pronounced shockwave in air. The designed polymers were tested
for an application as the polymer fuel in laser plasma thrusters.
Received: 21 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +41-56/3104-412, E-mail: thomas.lippert@psi.ch 相似文献
3.
Kasyutich V.L. Bale C.S.E. Canosa-Mas C.E. Pfrang C. Vaughan S. Wayne R.P. 《Applied physics. B, Lasers and optics》2003,76(6):691-697
We present an application of cavity-enhanced absorption spectroscopy with an off-axis alignment of the cavity formed by two
spherical mirrors and with time integration of the cavity-output intensity for detection of nitrogen dioxide (NO2) and iodine monoxide (IO) radicals using a violet laser diode at λ=404.278 nm. A noise-equivalent (1σ≡ root-mean-square variation
of the signal) fractional absorption for one optical pass of 4.5×10-8 was demonstrated with a mirror reflectivity of ∼0.99925, a cavity length of 0.22 m and a lock-in-amplifier time constant
of 3 s. Noise-equivalent detection sensitivities towards nitrogen dioxide of 1.8×1010 molecule cm-3 and towards the IO radical of 3.3×109 molecule cm-3 were achieved in flow tubes with an inner diameter of 4 cm for a lock-in-amplifier time constant of 3 s. Alkyl peroxy radicals
were detected using chemical titration with excess nitric oxide (RO2+NO→RO+NO2). Measurement of oxygen-atom concentrations was accomplished by determining the depletion of NO2 in the reaction NO2+O→NO+O2. Noise-equivalent concentrations of alkyl peroxy radicals and oxygen atoms were 3×1010 molecule cm-3 in the discharge-flow-tube experiments.
Received: 4 February 2003 / Revised version: 10 March 2003 / Published online: 12 May 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275-410, E-mail: vlk@physchem.ox.ac.uk 相似文献
4.
Düsterer S. Schwoerer H. Ziegler W. Salzmann D. Sauerbrey R. 《Applied physics. B, Lasers and optics》2003,76(1):17-21
The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation,
resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment
ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that
the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse
was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction
of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed
the influence of the prepulse on the EUV yield.
Received: 25 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/947-202, E-mail: duesterer@ioq.uni-jena.de 相似文献
5.
Strong blue photoluminescence from aligned silica nanofibers 总被引:1,自引:0,他引:1
L. Dai X.L. Chen J.K. Jian W.J. Wang T. Zhou B.Q. Hu 《Applied Physics A: Materials Science & Processing》2003,76(4):625-627
Photoluminescence (PL) and infrared spectra of aligned silica nanofibers are investigated. Two striking strong blue luminescence
emissions have been found at room temperature. This suggests that the silica nanofibers could be a candidate material for
a blue-light emitter. The intensity of the PL emission decreases after annealing, which can be interpreted as the decrease
of the oxygen deficiency resulting in the reduction of radiative recombination centers. Infrared spectra provide further evidence
of this conclusion, where the enhancement of Si–O absorption is observed in annealed samples.
Received: 2 October 2002 / Accepted: 7 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-10/8264-9531, E-mail: ldai@vip.sina.com 相似文献
6.
Costela A. García-Moreno I. Gómez C. Amat-Guerri F. Liras M. Sastre R. 《Applied physics. B, Lasers and optics》2003,76(4):365-369
We report on the laser action of modified dipyrromethene.BF2 complexes both dissolved in poly(methyl methacrylate) and copolymerized with methyl methacrylate. All recently synthesized
dyes have the chromophore core of laser dye pyrromethene 567, differing in the substituent in position 8. The new dyes showed
important and most significant increases in both lasing efficiency and photostability. When the laser samples were pumped
transversely at 534 nm, laser emission was obtained with efficiencies of over 30% in most cases, to be compared with a lasing
efficiency of 12% exhibited by reference dye pyrromethene 567 under the same experimental conditions. Some of the materials
exhibited highly photostable laser action, with no sign of degradation in the laser output after 60000 pump pulses at the
same position of the sample at a repetition rate of 10 Hz, whereas the laser emission of reference dye pyrromethene 567 dropped
to zero after less than 40000 pump pulses.
Received: 19 November 2002 /
Revised version: 20 February 2003 / Published online: 9 April 2003
RID="*"
ID="*"Corresponding author. Fax: +34-91/564-2431, E-mail: acostela@iqfr.csic.es 相似文献
7.
Experimental results pertaining to 1 ps pulse-width filaments at 248 nm are reviewed. The theoretical studies presented in
this paper show that scaling those filaments to ns pulse-widths should enable us to trap up to 1 J in a single channel. We
will show how the use of an aerodynamic window can lead to applications such as laser-induced lightning and high-aspect-ratio
hole drilling.
Received: 23 January 2003 / Accepted: 8 February 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505/277-4026, E-mail: jcdiels@unm.edu 相似文献
8.
F. Immler 《Applied physics. B, Lasers and optics》2003,76(5):593-596
Aerosols can introduce significant errors in measurements of trace gas concentration profiles with differential absorption
lidar (DIAL). Here, a solution to counteract the aerosol effect is introduced, which does not depend on additional measurements
and is applicable when absorption at the off-wavelength is not negligible. It is based on a numerical solution of the coupled
lidar equations and calculates the trace-gas concentration and the aerosol backscatter ratio simultaneously. Consequently,
most of the errors introduced by aerosols to DIAL measurements are inherently corrected and, additionally, the aerosol backscatter
profiles at the DIAL wavelengths are obtained.
Received: 23 December 2002 / Revised version: 24 March 2003 / Published online: 14 May 2003
RID="*"
ID="*"Corresponding author. Fax: +49-331/288-2178, E-mail: fimmler@awi-bremerhaven.de Present address: AWI Bremerhaven, Am
Handelshafen 12, 27570 Bremerhaven, Germany 相似文献
9.
D. Bäuerle R. Denk J.D. Pedarnig K. Piglmayer J. Heitz G. Schrems 《Applied Physics A: Materials Science & Processing》2003,77(2):203-207
Laser-induced material processing is reviewed with special emphasis on recent achievements mainly obtained by the Linz group.
Among those are investigations using optical fiber tips for nanoscale photophysical etching, laser-induced surface patterning
using self-assembled microspheres, the pulsed-laser deposition of thin films of high-temperature superconductors and the modification
and cleaning of surfaces.
Received: 7 February 2003 / Accepted: 6 March 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +43-732/2468-9242, E-mail: dieter.baeuerle@jku.at 相似文献
10.
G.D. Hager V.D. Nikolaev M.I. Svistun M.V. Zagidullin 《Applied Physics A: Materials Science & Processing》2003,77(2):325-329
Experimental results have demonstrated that the use of ejector-nozzle concepts can allow to achieve simultaneously high chemical
efficiency and high pressure recovery in a chemical oxygen iodine laser. The estimated small-signal gain of the gain medium
generated by these nozzle banks was from 0.5 to 0.8 %/cm. In laser experiments with all nozzle banks (NB-1–NB-5), Pitot pressures
of the order of 80 Torr and Mach numbers of ∼2 in the cavity-mixing chamber have been achieved. The geometry of a given ejector-nozzle
bank and gas-flow conditions affect the power extraction and chemical efficiency. The main factors for high efficiency and
high power are small mixing scale, high area for the oxygen flow, dilution of chlorine by helium, and the arrangement of nozzles.
A chemical efficiency of 25% at a power level of ∼900 W was obtained for NB-1 having the smallest mixing scale, parallel injection
of all flows, and dilution of oxygen by helium. The highest power of ∼1.2 kW with a chemical efficiency of 19.5% and 160 W/cm2 of specific output power was achieved with NB-5 having the largest area for the oxygen flow and dilution of oxygen by helium.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +7-8462/355-600, E-mail: nikolaev@fian.smr.ru 相似文献
11.
Giant field amplification in tungsten nanowires 总被引:5,自引:0,他引:5
Umnov A.G. Shiratori Y. Hiraoka H. 《Applied Physics A: Materials Science & Processing》2003,77(1):159-161
The original RF-sputtering-assisted technique to produce metal wires with tip-curvature radii at the nanometer scale was developed
and applied to tungsten. The wire tips were characterized by scanning electron microscopy. Field-emission tests of those wires
exhibit excellent performance and reliable processability. Very high field-amplification factors of 18000 were demonstrated.
Received: 1 November 2002 / Accepted: 30 November 2002 / Published online: 11 April 2003
RID="*"
ID="*"Corresponding author. Fax: +1-972/479-4482, E-mail: alexander.umnov@fla.fujitsu.com 相似文献
12.
V.V. Vassiliev S.M. Il’ina V.L. Velichansky 《Applied physics. B, Lasers and optics》2003,76(5):521-523
A miniature high-coherent diode laser was developed. Optical feedback from a high-Q microsphere resonator was used to narrow
the spectrum of the laser, and a nearly half-pitch gradient-index lens served as a coupling element. As estimated from the
variation in frequency-tuning range (chirp-reduction factor) the fast line width of the laser was reduced by more than three
orders. It is remarkable that the system reveals stable single-mode operation at a relatively high feedback level. A tentative
explanation is presented in terms of previously given models.
Received: 8 July 2002 / Revised version: 9 March 2003 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +7-095/334-0249, E-mail: vvv@okb.lpi.troitsk.ru 相似文献
13.
C.F. Wisniewski K.B. Hewett G.C. Manke II P.G. Crowell C.R. Truman G.D. Hager 《Applied Physics A: Materials Science & Processing》2003,77(2):337-342
The overtone gain medium of a small-scale HF overtone laser was probed using a sub-Doppler tunable diode laser. Two-dimensional
spatially resolved small signal gain and temperature maps were generated for several ro-vibrational transitions in the HF
(v=2→v=0) overtone band. Our results compare well with previous measurements of the overtone gain in a similar HF laser device.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505/846-4807, E-mail: kevin.hewett@kirtland.af.mil 相似文献
14.
V.G. Gudelev V.V. Mashko N.K. Nikeenko G.I. Ryabtsev A.B. Stalmashonak L.L. Teplyashin 《Applied physics. B, Lasers and optics》2003,76(3):249-252
Using the mode splitting that can be achieved by exploiting the effect of photoelasticity and the mode selection properties
of coupled resonators, single- and two-frequency operation of a diode pumped cw YAG:Nd3+ laser was observed. In the two-frequency case, a regime with two orthogonal linearly polarized modes was realized. The frequency
difference between the adjacent modes could be varied from 50 MHz to 8.4 GHz. A maximum laser output power of 12 mW was achieved
at a pump level of 240 mW .
Received: 1 November 2002 / Revised version: 14 January 2003 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +375-17/2840-879, E-mail: ryabtsev@dragon.bas-net.by 相似文献
15.
The use of continuum source and self-reversal background correction were investigated for flame molecular absorption spectrometry (MAS). Chloride was determined by MAS using the aluminum monochloride molecule in a conventional flame atomic absorption spectrometer. Absorbance of this molecule was monitored in a lean nitrous oxide/acetylene flame at 261.4 nm using a lead hollow cathode lamp as the excitation source. Characteristic masses of 210, 260, and 820 mg/L were observed for no background correction, continuum source correction, and self-reversal correction, respectively. The ability of the techniques to correct for interferences caused by high concentrations of fluoride and sodium was investigated. The self-reversal technique was shown to remove interferences at concentration levels up to 10,000 mg/L. Chloride was determined in chloroacetic acid using calibration with chloride standards; continuum source correction had the best recovery value. These results suggest that both correction methods should be investigated for practical applications of flame MAS to obtain optimum analytical performance. 相似文献
16.
Measurement of filament length generated by an intense femtosecond laser pulse using electromagnetic radiation detection 总被引:4,自引:0,他引:4
We present a new method to measure the length of a filament induced by the propagation of intense femtosecond laser pulses
in air. We used an antenna to detect electromagnetic pulses radiated from multipole moments inside the filament oscillating
at the plasma frequency. The results are compared with the values detected from the backscattered fluorescence induced by
multiphoton ionization of nitrogen molecules excited inside the filament. The values are found to be in good agreement.
Received: 6 November 2002 / Revised version: 27 January 2003 / Published online: 24 April 2003
RID="*"
ID="*"Corresponding author. Fax: +1-418/656-2623, E-mail: shosseini@phy.ulaval.ca 相似文献
17.
The temporal influence of a laser pulse on saturated laser-induced fluorescence is investigated by means of numerical solutions
of rate equations describing dynamical models of two- and four-level molecular systems. It turns out that temporal wings of
the laser become negligible if the saturated fluorescence power from the entire pulse is monitored instead of the total energy
obtained from the integrated fluorescence. The negligibility is evaluated relative to the saturation status obtained with
temporal sampling of the fluorescence signal as is commonly adopted in the time-resolved technique. The advantages and the
limitations of power measurements are discussed with reference to the experimental feasibility of pulse acquisitions for the
determination of the flawless saturation degree.
Received: 4 December 2002 / Revised version: 14 February 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +39-06/3048-4811, E-mail: michele.marrocco@casaccia.enea.it 相似文献
18.
D. Guo K. Cai Y. Huang L.-T. Li 《Applied Physics A: Materials Science & Processing》2003,76(7):1121-1124
This work reports a novel anti-spatter and anti-crack ceramic laser drilling method based on the gelcasting technique. A Nd:YAG
solid state laser was used to drill micro-holes directly on a gelcast green alumina body. The results reveal that the irregular
spatter at the periphery of the hole inherent to traditional laser drilling methods can be effectively prevented by direct
drilling of the gelcast green body. Much more regular hole shapes without microcracks were also successfully obtained.
Received: 02 October 2002 / Accepted: 07 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-10-62771160, E-mail: caikai99@mails.tsinghua.edu.cn 相似文献
19.
G. Kresse W. Bergermayer R. Podloucky E. Lundgren R. Koller M. Schmid P. Varga 《Applied Physics A: Materials Science & Processing》2003,76(5):701-710
Complex surface reconstructions and surface oxides, in particular, often exhibit complicated atomic arrangements, which are
difficult to resolve with traditional experimental methods, such as low energy electron diffraction (LEED), surface X-ray
diffraction (SXRD) or scanning tunnelling microscopy (STM) alone. Therefore, ab initio density functional calculations are
used as a supplement to the experimental techniques, but even then the structural determination usually relies on a simple
trial and error procedure, in which conceivable models are first constructed and then tested for their stability in ab initio
calculations. An exhaustive search of the configuration space is usually difficult and requires a significant human effort.
Solutions to this problem, such as simulated annealing, have long been known, but are usually considered to be too time-consuming
in combination with first principles methods. In this work, we show that ab initio density functional codes are now sufficiently
fast to perform extensive finite temperature molecular dynamics. The merits of this approach are exemplified for two cases,
for a complex two-dimensional surface oxide on Pd(111), and for the oxygen induced c(6×2) reconstruction of V(110).
Revised version: 15 July 2002 / Accepted: 2 October 2002 / Published online: 5 February 2003
RID="*"
ID="*"Corresponding author. Fax: +43-1/4277-9514, E-mail: Georg.Kresse@univie.ac.at 相似文献
20.
H. Teng J. Zhang Z.L. Chen Y.T. Li X. Lu K. Li X.Y. Peng 《Applied physics. B, Lasers and optics》2003,76(6):687-690
The plasma jet formed on the rear surface of a foil in laser–solid interaction is investigated by laser probing. The rear
plasma jet, which is in line with the laser, formed a few picoseconds after the incidence of the focused laser, is due to
a beam of fast electrons propagating through the target and is collimated by a strong magnetic field in the plasma.
Received: 14 January 2003 / Revised version: 2 April 2003 / Published online: 2 June 2003
RID="*"
ID="*"Corresponding author. Fax: +86-10/8264-9531 E-mail: jzhang@aphy.iphy.ac.cn 相似文献