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21.
An optical tilt sensor was developed and its performance was investigated. The tilt sensor set-up consisted of a laser light source, lenses and an image sensor. A precision reference tilt sensor was also installed on the same stage, and the measurement results of tilt angles using the optical and reference tilt sensors were correlated. The correlation coefficient (R-value) obtained under ideal conditions was 0.99454, indicating that the optical tilt sensor could produce as accurate measurements as the precision reference tilt sensor. The R-value decreased to 0.97714 and 0.93209 when the image sensor was shifted backwards and forwards from the focal plane by 1 mm, respectively. The R-value decreased to 0.96840 when the tilt sensor was performed with the room light turned on. There were not significant differences in the measurement results obtained with air conditioners turned on and off, indicating that the optical tilt sensor was robust and was not sensitive to the surrounding air turbulence. These findings are useful for the final design of the optical tilt sensor. 相似文献
22.
G.M. Koretsky M.B. Knickelbein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,2(3):273-278
The photoionization spectra of Pr2-Pr21 and Ce2-Ce17 have been measured near threshold. The ionization potentials (IPs) of and vary discontinuously with size, but trend downward toward the work function of the bulk metals. In general, the IPs of cerium
clusters display more variation than those of praseodymium clusters. The sudden discontinuities observed in the IPs of both
and is akin to that displayed by clusters of transition metal atoms, suggesting that as in transition metal clusters, the rapid
evolution in geometric structure with size is the source of these discontinuities.
Received: 2 January 1998 / Accepted: 10 March 1998 相似文献
23.
A phase-sensitive technique was used to measure the sensitivity to operating conditions of the output frequency of a highly stable carbon dioxide laser, which operated on the 10-μmm R(0) transition (28.8 THz) and was locked to the saturated absorption of the Q(15) transition of OsO4. Periodic changes in the operating conditions were imposed on the laser and the resulting changes in the output frequency were measured through phase-sensitive demodulation of the heterodyne beat with a second CO2 laser of much lower stability. Shifts as small as 50Hz could be detected by this technique. The results are in good agreement with previous measurements which employed an infrared frequency chain. 相似文献
24.
H.C. Mastwijk M. van Rijnbach J.W. Thomsen P. van der Straten A. Niehaus 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(2):131-137
This paper presents an experimental investigation of cold collisions between metastable helium atoms in an optical trap at
1 mK. Penning (PI) and associative (AI) ionization reactions are distinguished using a mass spectrometer and studied under
influence of near resonant laser light. Dramatic enhancement, by more than a factor 15, of the ion rate is observed when the
laser is tuned close to resonance. Experimental findings are well-described, on an absolute scale, by model predictions.
Received: 9 February 1998 / Revised: 4 May 1998 / Accepted: 14 May 1998 相似文献
25.
We observed frequency splitting phenomenon of dual transverse modes (TEM00q and TEM01q) in a Nd:YAG microchip standing wave laser utilizing intracavity stress birefringence effects. Four resonance frequencies (ν00qe, ν00qo, ν01qe, and ν01qo, respectively) were produced and tuned by changing the diametral compression force applied on the laser crystal. The transverse mode frequency spacing for the same longitudinal mode number (Δνtrans) was 1.16 GHz, and the magnitude of frequency splitting (Δν) ranged from 0 MHz to 1.16 GHz. Based on this phenomenon, a four-mode differential standing wave laser, whose signal characteristics were a little like those of a four-mode differential travelling wave laser gyro however with a much larger frequency splitting range, was produced. The theoretical analysis is in good agreement with the experimental results. This phenomenon not only can be used to make lasers with two or more frequency differences, but also can be used to make high-resolution self-sensing laser sensors (e.g. laser force sensors and laser accelerometers). 相似文献
26.
L. S. Pan H. P. Lee C. Lu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,50(1):27-33
We report the synthesis and measurement of an
ultra-precise and extremely stable optical frequency in the
telecommunications window around 1543 nm. Using a fibre-based femtosecond
frequency comb we have phase-stabilised a fibre laser at 194 THz to an
optical frequency standard at 344 THz, thus transferring the properties of
the optical frequency standard to another spectral region. Relative to the
optical frequency standard, the synthesised frequency at 194 THz is
determined to within 1 mHz and its fractional frequency instability is
measured to be less than 2×10-15 at 1 s, reaching 5×
10-18 after 8000 s. We also measured the synthesised frequency against
a caesium fountain clock: here the frequency comparison itself contributes
less than 4 mHz (2×10-17) to the uncertainty. Our results
confirm the suitability of fibre based frequency comb technology for
precision measurements and frequency synthesis, and enable long-distance
comparison of optical clocks by using optical fibres to transmit the
frequency information. 相似文献
27.
The temperature dependence of photoluminescence in Europium tris[3-(trifluoro-methylhydroxymethylene)-(+)-camphorate] (EuTFC) embedded in polymer films has been examined from 40 K down to 4.2 K with the goal of preparing sensor films for low-temperature thermal imaging. The behavior of EuTFC showed significant difference when based on polystyrene compared to poly(n-alkyl methacrylate)s. In poly(n-alkyl methacrylate)s prepared by standard methods for imaging applications, the photoluminescence is fully saturated below 30 K, whereas in polystyrene films there is a strong temperature dependence even down to 4.2 K. By optimizing the preparation procedure for films made of poly(butyl methacrylate) (PBMA) and poly(methyl methacrylate), also these polymers became very sensitive down to liquid helium temperature. The maximum temperature sensitivity of EuTFC in PBMA is found to be 1.0%/K at 4.2 K. The problem of delamination and cracking of the polymer film at cryogenic temperature is also avoided by the special preparation method. 相似文献
28.
We report the amorphization induced high magneto-caloric effect (MCE) of recently developed Gd55Al15Ni30 bulk metallic glass (BMG). The magnetic properties of the Gd55Al15Ni30 BMG are investigated in comparison with that of its crystalline counterpart. It is found that amorphization can increase the saturation magnetization and decrease the hysteresis of Gd55Al15Ni30 alloys, which indicate the possible enhancement of MCE. The magnetic entropy changes and the refrigerant capacity of the BMG as well as the crystalline samples is calculated directly from isothermal magnetic measurements. The results show the amorphization induced high MCE of the alloy and the excellent refrigerant efficiency of Gd55Al15Ni30 bulk metallic glass. 相似文献
29.
This work demonstrates a semi-automatic optical frequency counter based on two mode-locked fiber laser combs. The mode number
of the comb line involved in the optical frequency measurement is determined by operating the two laser combs at three different
repetition rates, with two of them similar enough to have the same mode number of the beating comb lines. The determination
of the mode number is independent of the frequency fluctuation of the laser under measurement. The whole measurement process
was automated, except for the frequency stabilization of the laser combs and the optimization of the beat signal–to–noise
ratio. 相似文献
30.
David Wisbey Yaroslav Losovyj A.N. Caruso John Belot Peter A. Dowben 《Applied Surface Science》2009,255(6):3576-3580
The effects of vacuum ultraviolet radiation on the adsorbed copper center molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (or Cu(CNdpm)2), (C24H36N2O4Cu, Cu(II)) was studied by photoemission spectroscopy. Changes in the ultraviolet photoemission spectra (UPS) of Cu(CNdpm)2, adsorbed on Co(1 1 1), indicate that the ultraviolet radiation leads to decomposition of Cu(CNdpm)2 and this decomposition is initially dominated by loss of peripheral hydrogen. 相似文献