共查询到20条相似文献,搜索用时 15 毫秒
1.
V.B. Tiwari S. Singh S.R. Mishra H.S. Rawat S.C. Mehendale 《Applied physics. B, Lasers and optics》2006,83(1):93-96
We report on a Doppler-free polarization spectroscopy based technique of laser frequency stabilization using a balanced bi-polarimeter
set-up. Two linearly polarized weak laser beams are used to probe birefringence induced by two oppositely circularly polarized
strong pump beams in a vapour cell. Subtraction of balanced polarimeter signals obtained from the two probe beams results
in a background-free dispersion-like reference signal without frequency modulation. The dispersion-like signal corresponding
to the closed transition 5 2
S
1/2 (F=2) →5 2
P
3/2 (F′=3) of 87Rb was used for frequency locking of a diode laser. The frequency fluctuations and the drift were measured to be less than
0.25 MHz and 0.02 MHz, respectively, for an observation period of more than 10 hours.
PACS 42.62.Fi; 42.55.Px; 32.30.-r 相似文献
2.
Marina Movsisyan Svetlana Shmavonyan Aram Papoyan 《Central European Journal of Physics》2011,9(4):948-955
We present the results of spectroscopic and polarization studies of dilute rubidium vapor exposed to a single-frequency linearly
polarized diode laser radiation in a spectral range of atomic D2 line. We report the origin of a circularly polarized radiation on V-type transitions of 87Rb F
g
= 2 → F
e
= 3 and 85Rb F
g
= 3 → F
e
= 4, and amplification of this radiation in backward direction caused by a partial population inversion among magnetic sublevels
of the ground and excited levels. This is confirmed experimentally by high directivity of backward radiation, absence in its
spectrum of 85Rb F
g
= 2 → F
e
= 1 (Λ-type) radiation, as well as by different nature of intensity dependences of backward and fluorescence radiations. 相似文献
3.
V. V. Skobelev 《Journal of Experimental and Theoretical Physics》1997,85(1):13-16
We consider axion formation processes in the synchrotron (e
−→e
−
a) and annihilation (e
−
e
+→a) channels in a constant crossed field F
μν
Fμν=Fμν*F
μν
=0, which approximates constant fields of other configurations in the ultrarelativistic asymptotic limit. The probability
and intensity of axion emission are obtained, and we analyze the energy and field asymptotics. A comparison with the characteristic
neutrino channel
yields the constraints on the axion mass and the energy scale for Peccei-Quinn symmetry breaking. Possible astrophysical
applications are discussed.
Zh. éksp. Teor. Fiz. 112, 25–31 (July 1997) 相似文献
4.
A differential thermal analysis ΔT
y
(T) in vacuum has been performed, and the temperature gradient ΔT
x
(T) along the Ag2Se sample during the transition α → β has been studied. It has been shown that the transitions α → α′ and β′ → β are displacive
transitions and that the transition α′ → β′ is a reconstructive transition. It has been found that the temperature gradient
along the sample during the transition α′ → β′ passes through a deep minimum due to a strong increase in the specific heat
capacity. 相似文献
5.
Ana Paula A. Marques Marcos Takashi S. Tanaka Elson Longo Edson R. Leite Ieda Lucia Viana Rosa 《Journal of fluorescence》2011,21(3):893-899
SrMoO4 doped with rare earth are still scarce nowadays and have attracted great attention due to their applications as scintillating
materials in electro-optical like solid-state lasers and optical fibers, for instance. In this work Sr1−xEuxMoO4 powders, where x = 0.01; 0.03 and 0.05, were synthesized by Complex Polymerization (CP) Method. The structural and optical
properties of the SrMoO4:Eu3+ were analyzed by powder X-ray diffraction patterns, Fourier Transform Infra-Red (FTIR), Raman Spectroscopy, and through Photoluminescent
Measurements (PL). Only a crystalline scheelite-type phase was obtained when the powders were heat-treated at 800 °C for 2 h,
2θ = 27.8° (100% peak). The excitation spectra of the SrMoO4:Eu3+ (λEm. = 614 nm) presented the characteristic band of the Eu3 + 5L6 transition at 394 nm and a broad band at around 288 nm ascribed to the charge-transfer from the O (2p) state to the Mo (4d)
one in the SrMoO4 matrix. The emission spectra of the SrMoO4:Eu3+ powders (λExc. = 394 and 288 nm) show the group of sharp emission bands among 523–554 nm and 578–699 nm, assigned to the 5D1→7F0,1and 2 and 5D0→7F0,1,2,3 and 4, respectively. The band related to the 5D0→7F0 transition indicates the presence of Eu3+ site without inversion center. This hypothesis is strengthened by the fact that the band referent to the 5D0→7F2 transition is the most intense in the emission spectra. 相似文献
6.
Steady state mode-locked operation of a neodymium laser operating on the 4F3/2 → 4I13/2 transition around 1.3 μm is achieved for the first time using transmitting single-walled carbon nanotube (SWCNT) saturable
absorber. The Nd:YVO4 laser cavity was optimized for large fundamental mode volume generating an average power of 0.8 W at a repetition rate of
127 MHz in a stable train of 16.5 ps long pulses. 相似文献
7.
A.V. Papoyan M. Auzinsh K. Bergmann 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(1):63-71
We report results of a theoretical and experimental study of the ground state nonlinear Hanle effect under strong laser excitation.
It is shown that besides the well-known zero-magnetic field suppression of absorption on F
g = F→F
e = F - 1 transitions caused by population trapping, an optical pumping induced enhanced absorption occurs on F
g = F→F
e = F + 1 transitions for small B-fields. The latter effect becomes more pronounced for high F values. The experiment with atomic vapor of Cs (D2 line, F
g = 4) confirms an increase of the spectrally unresolved fluorescence yield at zero magnetic field and 600 mW/cm2 laser intensity by 9% or 42%, when excitation occurs with linearly or circularly polarized light, respectively. The results
of the experiment agree with numerical simulation studies using equations of motion for a density matrix.
Received 24 November 2001 / Received in final form 25 March 2002 Published online 24 September 2002 相似文献
8.
The effect of temperature on the luminescence intensity of the two bands due to 5
D
1→7
F
1 and 5
D
0→7
F
1 transitions in Eu3+ on excitation with the 476.5 nm line from an Ar+ laser has been studied in tellurite and calibo glasses. It is interesting to note that the peak intensity of the 5
D
1→7
F
1 transition increases with increasing temperature where as that of the 5
D
0→7
F
1 transition decreases. The ratio of the intensities of the two bands have been used to estimate the temperature.
PACS 42.70 Ce 相似文献
9.
J. Dingjan B. Darquié J. Beugnon M.P.A. Jones S. Bergamini G. Messin A. Browaeys P. Grangier 《Applied physics. B, Lasers and optics》2006,82(1):47-51
We have constructed a pulsed laser system for the manipulation of cold 87Rb atoms. The system combines optical telecommunications components and frequency doubling to generate light at 780 nm. Using
a fast, fibre-coupled intensity modulator, we sliced output from a continuous laser diode into pulses with a length between
1.3 and 6.1 ns and a repetition frequency of 5 MHz. These pulses are amplified using an erbium-doped fibre amplifier, and
frequency-doubled in a periodically poled lithium niobate crystal, yielding a peak power up to 12 W. Using the resulting light
at 780 nm, we demonstrate Rabi oscillations on the F=2,mF=+2↔F′=3, m′
F=+3-transition of a single 87Rb atom.
PACS 32.80.Qk; 39.25.+k; 42.55.-f 相似文献
10.
In the context, a modified sol-gel technology was afford to the synthesis of rare earth composite ceramic phosphors MM′O3/CeO2 and MM′O3/CeO2: Pr3+ (M = Ca, Sr; M′ = Ti, Zr) with multicomponent hybrid precursors were composed. The micromorphology, particle size and photoluminescence
properties were studied with XRD, SEM and luminescent spectroscopy in detail. Both XRD and SEM indicated the particle sizes
were in the submicrometer range of 100 ∼ 300 nm. The photoluminescence for these ceramic phosphors were studied in details
with the different component of host (molecular ratio of Sr, Ca and Ti, Zr), presenting a broad spectral band in the visible
blue-violet region with the maximum excitation peak at 449 nm and a wide emission range with a maximum peak at 619 nm, which
was ascribed to be the characteristic transition of Pr3+ (1D2 → 3H4). These phosphors can be expected for visible light conversion (blue → red) materials. Especially it can be found that the
introduction of CeO2 can enhance the luminescence intensity of MM′O3 and MM′O3: Pr3+. 相似文献
11.
P. Rosenbusch 《Applied physics. B, Lasers and optics》2009,95(2):227-235
We investigate the hyperfine transition of magnetically trapped non-condensed atoms. The two principal frequency shifts, the
second order Zeeman effect and the mean field interaction are considered. Analytic models of the mean frequency and its trap
induced spread are developed. Comparisons with existing experiments evaluate the role of the atoms’ oscillatory motion. The
analytic model proves to be equivalent to existing Monte Carlo simulations. The formulae provide a simple tool for optimising
the design of a new experiment. Applied to the two-photon transition |F=1,m
F
=−1〉→|F=2,m
F
=1〉 in 87Rb and the conditions of a typical atom chip experiment, a line spread as small as 11 mHz is predicted giving a quality factor
of 1012. The system is promising for application in precision instruments such as compact atomic clocks. 相似文献
12.
The recently discovered narrow peaks (theψ-particles) in e+e− system at 3.105 and 3.695 GeV are interpreted as hadrons in a broken SU4 symmetry scheme. A new additional additive quantum number, parachargeZ, is combined with the usual SU3 quantum numbers in the group SU4. Theψ (3.1) is assigned to a near ideally mixed15⊕1 multiplet of vector mesons (containing theρ) as theI=Y=0, charge conjugationC=−combination ofZ=±1.members. Theψ (3.7) is assigned correspondingly to another mixed15⊕1 multiplet containing theρ′ (1600). The hadronic electromagnetic interactions are modified by the addition of (non-minimal) anomalous pieces that can
changeZ. The decays of theψ-particles are discussed. New enlarged SU4 multiplets of other hadrons are proposed. Tests of our scheme are put forward. The most crucial test will be the observation
of two rather broad resonances in e+ e− collisions with masses around 4.2 GeV and 5.1 GeV. Another prediction is the presence of energetic photons in the decays
of theψ-particles. Important results concerning the recently observed phenomena in the process e+e−→hadrons follow in this scheme. 相似文献
13.
D. V. Brazhnikov A. V. Taichenachev A. M. Tumaikin V. I. Yudin I. I. Ryabtsev V. M. Entin 《JETP Letters》2010,91(12):625-629
A polarization method has been proposed for transforming the nonlinear electromagnetically induced transparency resonance
into the electromagnetically induced absorption resonance (and vice versa) in the Hanle configuration in the field of counterpropagating
waves. Numerical calculations have been performed for the F
g = 2 → F
e = 1 and F
g = 2 → F
e = 3 transitions in the 87Rb atom. The qualitative analysis of the effect has been performed for the three-level Λ scheme of the atomic energy levels.
The main theoretical conclusions are in qualitative agreement with our experimental data for 87Rb. The results can be applied in magnetometry and nonlinear optics. 相似文献
14.
Using the data of about 33 pb-1 collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied the exclusive semileptonic
decays D+→K-π+e+νe, D0→K̄0π-e+νe, D+→K̄*0e+νe and D0→K*-e+νe. The absolute branching fractions for the decays are measured to be BF(D+→K-π+e+νe)=(3.50±0.75±0.27)%, BF(D0→K̄0π-e+νe)=(2.61±1.04±0.28)%, BF(D+→K̄*0e+νe)=(5.06±1.21±0.40)% and BF(D0→K*-e+νe)=(2.87±1.48±0.39)%. The ratio of the vector to pseudoscalar semileptonic decay rates Γ(D+→K̄*0e+νe)/Γ(D+→K̄0e+νe) is determined to be 0.57±0.17±0.02. 相似文献
15.
A. E. Dorokhov 《Physics of Particles and Nuclei Letters》2010,7(4):229-234
Experimental and theoretical progress concerning the rare decay π0 → e
+
e
− is briefly reviewed. It includes the latest data from KTeV and a new model-independent estimate of the decay branching which
show the deviation between experiment and theory at the level of 3.3σ. The predictions for η and η′ decays into lepton pair
are presented. We also comment on the impact on the pion rare decay estimate of the data of BABAR collaboration on the pion
transition form factor at large momentum transfer. 相似文献
16.
XiaoBo Chen ZengFu Song JinGuang Wu N. Sawanoboi M. Ohtsuka YongLiang Li Jing Zhou Ce Wang JinYing Liu Qiang Tian Ping Sun HongMei Jing 《中国科学G辑(英文版)》2008,51(12):1868-1876
The ultraviolet upconversion luminescence of Tm3+ ions sensitized by Yb3+ ions in oxyfluoride nanophase vitroceramics when excited by a 975 nm diode laser was studied. An ultraviolet upconversion
luminescence line positioned at 363.6 nm was found. It was attributed to the fluorescence transition of 1D2→3H6 of Tm3+ ion. Several visible upconversion luminescence lines at 450.7 nm, (477.0 nm, 462.5 nm), 648.5 nm, (680.5 nm, 699.5 nm) and
(777.2 nm, 800.7 nm) were also found, which result respectively from the fluorescence transitions of 1D2→3F4, 1G4→3H6, 1G4→3F4, 3F3→3H6 and 3H4→3H6 of Tm3+ ion. The careful measurement and analysis of the variation of upconversion luminescence intensity F as a function of the 975 nm pumping laser power P prove that the upconversion luminescence of 1D2 state is partly a five-photon upconversion luminescence, and the upconversion luminescence of 1G4 state and 3H4 state are respectively the three-photon and two-photon upconversion luminescence. The theoretical analysis suggested that
the upconversion mechanism of the 363.6 nm 1D2→3H6 upconversion luminescence is partly the cross energy transfer of {3H4(Tm3+), 3F4(Tm3+), 1G4(Tm3+)→1D2(Tm3+)} and {1G4(Tm3+)→3F4(Tm3+), 3H4(Tm3+)→1D2(Tm3+)} between Tm3+ ions. In addition, the upconversion luminescence of 1G4 and 3H4 state results respectively from the sequential energy transfer {2F5/2(Yb3+)→2F7/2(Yb3+), 3H4(Tm3+)→1G4(Tm3+)} and {2F5/2(Yb3+) →2F7/2(Yb3+), 3F4(Tm3+)→3F2(Tm3+)} from Yb3+ ions to Tm3+ ions.
Supported by the National Natural Science Foundation of China (Grant No. 10674019) 相似文献
17.
We investigate the potential of eγ collisions to probe anomalous Wtb couplings via the polarized single top quark production
process e+γ→tb̄νē. We find 95% confidence level limits on the anomalous coupling parameters F2L and F2R with an integrated luminosity of 500 fb-1 and , 1 and 1.5 TeV energies. The effects of top quark spin polarization on the anomalous Wtb couplings are discussed. It is shown
that polarization leads to a considerable improvement in the sensitivity limits.
PACS 14.65.Ha; 13.88.+e 相似文献
18.
The production of electron-positron pairs by a photon propagating in a thermal bath in both zero and strong (B ≫ 4.41 × 1013 G) magnetic fields has been considered. The mean free path has been calculated for the high-energy photon propagating through
a thermodynamically equilibrium photon gas along the magnetic field lines so that the γ → e
−
e
+ decay is kinematically forbidden. It has been shown that the strong magnetic field suppresses the probability of the γγ′
→ e
−
e
+ process. The analyzed process can be useful for analysis of possible mechanisms of the generation of the e
−
e
+ plasma in the regions of the polar caps of magnetars. 相似文献
19.
Iko Hyppänen Jorma Hölsä Jouko Kankare Mika Lastusaari Laura Pihlgren Tero Soukka 《Journal of fluorescence》2011,21(3):963-969
Up-converting NaRF4-NaR′F4 (R: Y, Yb, Er) nanomaterials with different core-shell combinations were prepared with the co-precipitation method. The X-ray
powder diffraction (XPD) measurements revealed the presence of both the cubic and hexagonal NaRF4 phases. The crystallite sizes calculated with the Scherrer formula were 100 and 150 nm for the cubic and hexagonal phases,
respectively. The FT-IR spectra showed water impurities. The up-conversion luminescence and luminescence decays were studied
with NIR laser excitation at 970 nm. The up-conversion luminescence spectra showed strong red (640–685 nm) (4F9/2 → 4I15/2) and moderate green (515–560 nm) (2H11/2,
4S3/2 → 4I15/2) Er3+ luminescence. The strongest up-conversion luminescence and longest red luminescence decay was obtained from the Na(Y,Yb)F4-NaErF4 core-shell combination. 相似文献
20.
《The European Physical Journal C - Particles and Fields》2006,48(3):767-780
Using a sample of over 400 million φ→KSKL decays produced during the years 2001 and 2002 at the DAΦNE e+e- collider, the ratio RS
π=Γ(KS→π+π-(γ))/Γ(KS→π0π0) has been measured with the KLOE detector. The result is RS
π=2.2555±0.0012stat±0.0021corr-stat±0.0050syst, which is in good agreement with the previously published result based on the KLOE data sample from the year 2000. The average
of the KLOE results is RS
π=2.2549±0.0054, reducing the total error by a factor of three, to 0.25%. 相似文献