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1.
The pressure dependence of the soft modes in the paraphase (boundary of the Brillouin zone, X point) and the ferrophase (center of the Brillouin zone, Γ point) is studied in the model ferroelastic crystals Hg2I2. An anomalous linear pressure dependence of the soft-mode frequency in the paraphase (p<p
c
) is observed. The results obtained and the nature of the ferroelastic phase transition induced in Hg2I2 crystals by a high hydrostatic pressure are discussed.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 227–231 (25 February 1996) 相似文献
2.
V. V. Antsiferov 《Technical Physics》1998,43(10):1203-1208
Experimental results are presented on the achievement of single-frequency tunable lasing in ruby, Nd-glass, and Nd:YAG lasers
with electrooptic Q switching of the cavity by the injection of an external signal. An optimization of the parameters is carried out for lasers
on neodymium ions in yttrium aluminum garnet, lanthanum beryllate, chromium-doped gadolinium scandium gallium garnet, and
lanthanum hexaaluminate with passive Q switching of the cavity by means of lithium fluoride shutters containing F
2
−
color centers. High-power single-frequency generation of giant pulses is achieved, with the output wavelength tunable over
the half-width of the gain lines of the active media.
Zh. Tekh. Fiz. 68, 74–79 (October 1998) 相似文献
3.
A jump in the frequency of the quasiferromagnetic soft mode in Fe3BO6 at the point of the spontaneous orientational phase transitions Γ2−Γ4 is observed experimentally. It is shown theoretically that this jump can be explained by the contribution of the dipole interaction
to the expression for the quasiferromagnetic soft mode.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 356–359 (10 September 1999) 相似文献
4.
B. Bakowski G. Hancock R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2006,82(1):123-131
The absolute concentration and translational temperature of the 2p10 and 2p7 excited states of argon have been measured in an inductively coupled plasma chamber under a variety of operating conditions
using both calibrated diode laser frequency modulation spectroscopy and cavity enhanced absorption spectroscopy. Accurate
lineshape analysis of frequency modulation signals has been employed to extract the desired information, and is corroborated
by cavity enhanced measurements. Temperatures are found to vary linearly with pressure from ∼400 K at 20 mTorr (2.7 Pa) to
∼510 K at 90 mTorr (12 Pa) in a 200 W discharge while concentrations peak at 3.25×108 cm-3 at 30 mTorr (4 Pa) (also in a 200 W discharge). The uncertainty in the recovered temperature is 7%, dominated by uncertainties
in the calibration of the frequency scale.
PACS 42.62Fi; 52.70kz 相似文献
5.
A. Akrap R. Gaal L. Forró 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):287-291
We investigate the pressure and temperature behavior of current-dependent resistivity of β-SrV6O15. We observe a switching between states of different resistivities in the insulating state of β-SrV6O15. In the low pressure phase, the resistive switching appears at temperatures below the semiconductor-insulator transition.
In the high pressure phase, under ~1.6 GPa, the switching appears in the temperature range of the phase transition. The existence
of switching may imply an important role of strontium off-stoichiometry for the electrical transport in β-SrV6O15. No electric-field-induced enhancement of the conductivity is observed. However, the conduction is significantly nonlinear
under ~1.6 GPa, indicating that the charge order pattern in the high pressure phase is considerably different from that of
the low pressure phase. 相似文献
6.
H. Weiss M. V. Kartsovnik W. Biberacher E. Steep A. G. M. Jansen N. D. Kushch 《JETP Letters》1997,66(3):202-207
The interlayer magnetoresistance of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2)Br is measured at ambient pressure and under pressures of up to 12.5 kbar. In addition to the slow Shubnikov-de Haas oscillations
with a frequency of ≃150 T observed at P⩾5 kbar, rapid oscillations attributed to the magnetic breakdown orbit enveloping an area equal to 100% of the area of the
Brillouin zone are found to emerge above B=20 T. The latter oscillations are observed at ambient pressure as well as under pressures of up to 9 kbar.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 190–194 (10 August 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
7.
Based on calculations and experiments, a He–Ne laser has been developed with effective intracavity magnetooptical modulation
at λ = 1.15 μm. A polarization-anisotropic element — a magnetic diffraction grating made of yttrium iron garnet — is mounted
in a matched passive arm of the triple-mirror cavity of the laser and serves as the modulator element. Modulation is produced
using the Faraday effect, which simultaneously leads to efficient diffraction of the laser radiation on the asymmetric strip
domain structure of a magnetic diffraction grating and to rotation of the E vector. The Jones matrix method is used to calculate the frequency and polarization characteristics. These, along with the
modulation characteristics, were also studied experimentally. It is shown that amplitude modulation at frequencies up to 180 kHz
takes place for small single-pass Faraday rotation angles (θF). The threshold frequency is determined by the response time of the magnetizing Helmholtz coil. The depth of modulation is
50%. For θF > θt (where θt is the threshold), frequency modulation takes place with a deviation of up to several megahertz.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 188–193, March–April, 2009. 相似文献
8.
Electrical switching has been observed ino-tolidine-DDQ at pressures of 7.66 GPa and fields ∼3×105
V/m withσ
ON/σ
OFF≈103 at a temperature of 300 K. The switching is found to be of the memory type and the sample can be driven back to the low conducting
state by applying ac pulses of sufficient magnitude but independent of frequency. 相似文献
9.
I. I. Kalikinskii 《Technical Physics》1998,43(2):247-248
The energy of the radiation emitted by an ultrarelativistic (1 GeV) electron at a transition from vacuum into yttrium iron
garnet I3Fe5O12 at the ferromagnetic resonance frequency (vacuum wavelength 3 cm) is estimated. The energy at this frequency was found to
be 10−13 eV·s. If modern electron accelerators are used (particle current 10 mA), then for 1 s the energy at the ferromagnetic resonance
frequency will be of the order of 1 J·s, so that the effect could have practical applications.
Zh. Tekh. Fiz. 68, 122–123 (February 1998) 相似文献
10.
The compound acoustic resonator method is used to study the phenomenon of the ferrobielastic transition in single crystals
of quartz subjected to uniaxial pressure. Toward this end, a layered structure consisting of an aluminum film/zinc oxide film/aluminum
film sandwich was deposited on one of the surfaces of an X-cut plane-parallel quartz plate. This structure served as an electromechanical transducer in such a way that the entire system
acted as a multifrequency acoustic resonator. Uniaxial pressure was applied perpendicular to the direction of propagation
of the acoustic waves and caused a growth of the frequencies of the resonance peaks of the structures, indicating a change
in the velocity of the acoustic waves. The ferrobielastic phase transition, which arises at some threshold pressure (the ferrobielastic
switching effect), is characterized by a discontinuous drop in the frequencies of the resonance peaks. The variation of the
resonator frequency both below and above the switching threshold correlates with the variation of the so-called “natural”
sound velocity determined by the pressure-dependent elasticity constants of the material. The observed frequency jump of the
resonance peaks is due mainly to the relatively abrupt change in the dimensions of the crystal. The results of the acoustic
measurements allow reliable recording of the switching effect and a study of its properties.
Fiz. Tverd. Tela (St. Petersburg) 39, 290–294 (February 1997) 相似文献
11.
The existence of surface polaritons in a dielectric at a boundary with an ideal metal or superconductor in a static electric
field is predicted. The frequency regions in which polaritons exist are substantially different for opposite orientations
of the electric field, so that a change in the direction of the field signifies “switching on” or “switching off” of surface
polaritons with a fixed frequency.
Pis'ma Zh. éksp. Teor. Fiz. 68, No. 12, 876–880 (25 December 1998) 相似文献
12.
A theoretical study is carried out of quantum beats (QB) in the time-dependent intensities of absorption of a test pulse and
of spontaneous luminescence in a Cu2O crystal under conditions of double optical resonance. It is assumed that pumping is effected by a CO2-laser pulse which dynamically couples the exciton levels 1s(Γ
5
+
) and 2p(Γ
4
−
,Γ
5
−
,Γ
3
−
Γ
2
−
) and splits them into two or three pairs of quasi-energy levels. The frequency of the test pulse is in resonance with the
frequency Γ
5
+
of the exciton. The corresponding intensities for various directions of the electric vector of the pump field E
L, the polarization vector ξ, and the wave vector q of the test pulse are obtained. The frequency of the quantum beats is twice the Rabi frequency, which for different values
of E
L, ξ and q contains different sets of matrix elements of the dipole transitions between the levels 1s(Γ
5
+
) and 2p(Γ
4
−
,Γ
5
−
,Γ
3
−
Γ
2
−
). Thus, by measuring the period of the quantum beats it is possible to determine the unknown matrix elements of the indicated
transitions.
Fiz. Tverd. Tela (St. Petersburg) 39, 844–847 (May 1997) 相似文献
13.
S. A. Buiko S. M. Kulikov V. N. Novikov S. A. Sukharev 《Journal of Experimental and Theoretical Physics》1999,89(6):1051-1054
Stimulated Brillouin scattering (STBS) and phase conjugation of CO2 laser radiation have been demonstrated experimentally for the first time in compressed xenon (59 atm at 21°C) located inside
the low-Q cavity of this laser. The nonlinear medium was exposed to the action of counterpropagating focused multimode radiation
beams. The difference between the frequencies of the longitudinal cavity modes was set at the frequency of the acoustic wave
(v
s=32.2±0.3 MHz) excited as a result of STBS by 9.584 μm radiation. The duration of the radiation pulse τ
L was close to the acoustic phonon lifetime (τ
L<τ
ph≈3× 10−6s). The excitation of STBS was manifested experimentally as the locking of longitudinal modes, an increase in power and energy,
and also an increase in the duration of the lasing pulse and a reduction in the divergence to the diffraction limit.
Zh. éksp. Teor. Fiz. 116, 1941–1946 (December 1999) 相似文献
14.
15.
Abstract Y(Co1-xAlx)2 is a weak itinerant ferromagnet for 0.12 < x < 0.20 with a maximum Curie point of about 25 K near x = 0.15. The pressure dependence of the Curie point for samples with 0.14 < x < 0.18 was measured in the temperature and pressure range 5–25 K and 0–8 kbar using a liquid filled lock cell. It was found that Tc was linear in pressure and extrapolated to OK at Pc = 9 ± 1 kbar for all samples. The volume expansion from YCo2 to x = 0.15 is equivalent to a chemical pressure of -40 kbar so ferromagnetism cannot occur at the lattice constant of YCo2. 相似文献
16.
Highly ionically conducting amorphous samples of Ag2S·xSb2S3 (x=0.15−0.40) are mechanochemically synthesized and characterized by X-ray diffraction (XRD), DTA/DSC, electrical and electrochemical
methods. The electrical conductivity measurements are carried out as a function of frequency (5 Hz – 13 MHz) and temperature
(300 – 380 K). While the ac conductivity of x=0.40 composition obeys the well-known power law σ (ω)=σ (0) + A ωn over the whole frequency range, the x=0.30 sample obeys the above relation only at lower temperatures. The compositions x=0.20
and 0.15 do not follow the famous dispersion relation at higher (MHz) frequencies. The conductivity isotherms of these a-SICs
do not superimpose upon application of Summerfield scaling. The scaling behaviour and the variation of ac conductivity with
frequency for x=0.20 and 0.15 are explained in terms of switching from the predominantly ionic (at lower frequencies) to the
predominantly electronic conduction (at higher frequencies).
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Channai, India, Nov. 28–30, 2003. 相似文献
17.
H. Stoehr N. Rehbein A. Douillet J. Friebe J. Keupp T.E. Mehlstäubler H. Wolff E.M. Rasel W. Ertmer J. Gao A. Giesen 《Applied physics. B, Lasers and optics》2008,91(1):29-33
We have developed a Nd:YVO4 thin-disk laser at 914 nm with single-frequency operation and active frequency stabilization to a low-finesse reference cavity.
The spectral density of laser frequency noise is analysed by means of noise measurements at the error point of the frequency
control loop. To address the 31S0→33P1 magnesium intercombination line at 457 nm, we use an external frequency doubling stage based on periodically poled KTiOPO4 for the generation of more than 150-mW output power at 457 nm. Optical beat signal measurements at 457 nm with a frequency-stable
dye laser show a short-time line width of the thin-disk laser of less than 100 kHz.
PACS 42.55.Xi; 42.60.Lh; 42.62.Fi; 42.65.Ky 相似文献
18.
A study is made of the production of high power nanosecond rf pulses by extracting microwave energy from an oversized cavity
by means of conversion, at a coupling window, of the high-Q working mode to an auxiliary mode which is strongly coupled to
an external load. It is shown that microwave rf pulse compressors with copper storage cavities and energy extraction by mode
conversion at a coupling window can provide gains of 5–13 dB with output signal durations of 20–150 ns and peak powers of
5–10 MW in the 3-cm band and 50–100 MW in the 10-cm band. Rf pulses lasting 30 ns with peak powers of 0.5 MW have been obtained
experimentally at a frequency of 9.4 GHz with a gain of 9 dB.
Zh. Tekh. Fiz. 68, 92–96 (July 1998) 相似文献
19.
I. O. Bashkin M. V. Nefedova V. G. Tissen E. G. Ponyatovskii 《Physics of the Solid State》1998,40(12):1950-1952
The pressure dependence of the superconducting transition temperature in TiD0.74 has been measured up to 30 GPa in a diamond high-pressure chamber. It is found that the deuteride TiD0.74 becomes a superconductor at pressures corresponding to the transition to the high-pressure ζ phase, with a transition temperature that increases from 4.17 to 4.43 K in the interval P=14–30 GPa. The value extrapolated to atmospheric pressure T
c
(0)=4.0 K is significantly lower than the superconducting transition temperature (T
c
=5.0 K) measured earlier in the metastable state obtained by quenching TiD0.74 under pressure. It is assumed that the significant difference of the extrapolated value from the superconducting transition
temperature in the metastable state after quenching under pressure is caused by a phase transition on the path from the stability
region of the ζ phase under pressure to the region of the metastable state at atmospheric pressure.
Fiz. Tverd. Tela (St. Petersburg) 40, 2153–2155 (December 1998) 相似文献
20.
2 laser standards. Using this technique, we can tune the CO laser frequency with absolute frequency control within the gain
profile of each laser transition. The frequency uncertainty is smaller than 15 kHz, corresponding to Δν/ν=2.5×10-10. Moreover, we obtain a reduction of the CO laser linewidth by a factor of 2 down to 65 kHz, corresponding to a spectral resolution
of δν/ν=1×10-9. With this outstanding accuracy and resolution we studied the shape of saturation dips in rovibrational lines of CO and carbonyl
sulfide (OCS) at low pressure (<5 Pa). The self-pressure-broadening rate of CO was found to be γc=+83(7) kHz/Pa in this pressure region. This value is about four times higher than values resulting from previous measurements
at much higher pressures. To our knowledge the measurements described here are the first line-shape studies with sub-Doppler
resolution in the 5 μm spectral region.
Received: 4 November 1996 相似文献