铯原子调制转移光谱在激光稳频中的应用

利用铯原子D₂线的调制转移光谱的鉴频特性,实现了光栅外腔式主振荡器-功率放大型(MOPA)半导体激光器相对于铯原子6²S_1/2F=4→6²P_3/2 F’=5超精细跃迁的偏频锁定,在100 ms内激光频率的相对起伏小于±280 kHz.相对于一般的饱和吸收锁频方法而言,调制转移光谱在锁频中的应用不仅彻底消除了Doppler背景对锁频的影响,而且还避免了对激光器直接进行频率扰动而带来的附加频率噪音.     

Stark interaction for excited states in alkali atoms,investigated by laser spectroscopy

The scalar polarizability constantα ₀ for excitedS- andD-states in rubidium and cesium was measured utilizing a two-step excitation scheme. An rf lamp and a single-mode dye laser were used to excite the atoms in a collimated atomic beam. Values ofα ₀ were determined for the 9–10² S _1/2 and 7–8² D _3/2 states of rubidium and for the 10–13² S _1/2, 9–10² D _3/2 and 9–11² D _5/2 states of cesium. Further, the isotope shift was evaluated in the 5579 Å rubidium line. A review of experimental polarizability constants for rubidium and cesium is given, and the results are compared with theoretical values.     

Hyperfine splitting and isotope shift in the atomic D2 line of 22,23Na and the quadrupole moment of 22Na

The hyperfine structure of the D₂ optical line in ²²Na and ²³Na has been investigated using high resolution laser spectroscopy of a well-collimated atomic beam. The hyperfine splitting constants A and B for the excited 3p ²P_3/2 level for both investigated sodium isotopes have been obtained. They are as follows: A(22) = 7.31(4) MHz, B(22) = 4.71(28) MHz, A(23) = 18.572(24) MHz, B(23) = 2.723(55) MHz. With this data, using the high precision MCHF calculations for the electric field gradient at the nucleus, the electric quadrupole moment of ²²Na has been deduced: Q_s(22) =+0.185(11) b. The sign of Q_s(22), determined for the first time, indicates a prolate nuclear deformation. A precise value of the isotope shift ^22,23Na in the D₂ line has also been obtained. Received: 26 February 1998 / Revised version: 25 June 1998     

Raman scattering in FeF3

Peaks in the FeF₃ phonon Raman spectrum are assigned to the A_1g(312 cm^-1) and E_g(105, 187, 450 cm^-1) representations of the D⁶_3d group. Anomalous temperature dependence of the frequency, intensity and line width of the 187 cm^-1 line has been observed.     

High resolution measurement and MQDT analysis of the 5d<Superscript>9</Superscript> 6s<Superscript>2</Superscript> np,nf (J = 1) autoionizing resonances of mercury

We report new high resolution photoabsorption measurements of the 5d-subshell excitation spectra of mercury using a 3-meter normal incidence spectrograph equipped with a 6000 line/mm holographic grating and synchrotron radiation emitted by the Bonn 2.5 GeV electron accelerator as the background source of continuum. The observed spectra reveal autoionizing resonances attached to the 5d⁹(²D_5/2)6s² and 5d⁹(²D_3/2)6s² parent ion levels of mercury. We have analysed the line shapes of the lower members of the 5d⁹6s² np and nf J = 1 autoionizing resonances using the phase shifted formulation of the MQDT and extracted the interaction parameters.     

用高压显微光谱系统研究(Zn0.85Cd0.15)S:Cu,Al磷光体在流体静压力下施主-受主对的发光

用金刚石对顶砧高压显微光谱系统在室温和1bar—66kbar的流体静压力范围内研究了(Zn_0.85Cd_0.15)S:Cu,Al磷光体的发光峰位置和相对发光强度随压力而变化的规律。随着压力的增加,发射峰值波长迅速移向短波方向,而发射峰值对应的光子能量随压力增加的速率为4.7meV/kbar(38cm^-1/kbar)。这个值比该材料的吸收边随压力增加的速率要小。随着压力的增加,该磷光体的发光峰值相对强度急骤下降,当压力从常压升到66kbar时,发光峰值相对强度下降到原值的6％。这些结果可以用Al³⁺-Cu⁺的施主-受主对模型来解释。本文还估计施主(Al³⁺)和受主(Cu⁺)的激活能之和随压力增加的速率为3.7meV/kbar(30cm^-1/kbar)。 关键词：     

Saturation spectroscopy of ultraviolet transitions in mercury with a frequency-doubled cw ring dye laser

Doppler-free saturated absorption spectroscopy has been used to study the ultraviolet HgI transitions 6³P₀-6³D₁ at 296.73 nm and 6³P₀-6¹D₂ at 296.76 nm. The required tunable ultraviolet radiation was produced by a ring cavity cw dye laser with intracavity ADA frequency doubler. The isotope shifts of the 6³P⁰ -6³D₁ line for naturally abundant mercury have been measured to within a few MHz.     

Frequency stabilization of a laser diode to hyperfine structure of the 4D5/2 state of Rb atoms

We observed hyperfine structures of the 4D_5/2 state of ⁸⁵Rb atoms and applied them to the frequency stabilization of a laser diode by using the double resonance optical pumping (DROP). The hyperfine structures of the 4D_5/2 states of ⁸⁵Rb atoms were highly resolved in the Rb vapor cell. We compared the DROP with the optical-optical double resonance (OODR) in the 5S_1/2-5P_3/2-4D_5/2 ladder-type system of ⁸⁵Rb atoms. When we stabilized the frequency of a laser diode to the hyperfine structure of the 5P_3/2(F″ = 4)-4D_5/2(F″ = 3) transition by using the DROP spectrum, the frequency stability was approximately 2.3 × 10^− 12 after 100 s.     

Selective laser pumping of magnetic sublevels in the hyperfine structure of the cesium atom

The evolution of the populations of the magnetic sublevels of the cesium atom (¹³³Cs isotope) in resonant laser fields with linear polarization is analyzed using the equations for the density matrix. Analytic expressions are derived for stationary populations resulting from laser-induced optical transitions on the hyperfine structure components F _g = 3 ? F _e = 2, 3 and F _f = 4 ? F _e = 3, 4 of lines D ₁ (6² S _1/2 → 6² P _1/2) and D ₂ (6² S _1/2 → 6² P _3/2) depending on the initial values of the populations. The numerical solution of the evolution equations gives the characteristic times of stabilization of the steady regime as functions of laser field intensities and detuning from optical resonance. We determine the sequences of optical transitions increasing (by more than an order of magnitude) the population of the lower sublevel 6² S _1/2 F _g = 3 M = 0 of the “clock” microwave transition F _g = 3 M = 0 ? F _f = 4 M = 0 in the cesium frequency standard, which increases the signal intensity in the recording system by the same proportion.     

Bestimmung derP 3/2 —D 3/2-Aufspaltimg und Nachweis von crossing-Signalen im Zustandn=3 von ionisiertem Helium

Radio frequency induced transitions between 3D _5/2- and 3P _3/2-Zeeman sublevels in He⁺ have been detected. From the position of the line center of theD _5/2 (m=?1/2)—P _3/2(m=1/2) transition, the splittings 3D _5/2—3P _3/2=(17259±13) MHz and 3P _3/2—3D _3/2=(81±13) MHz have been deduced. The theoretical values are 17254.9 and 85.4 MHz. Three crossings of Zeeman sublevels of the 3S-, 3P- and 3D-states of He⁺ have been detected both by a magnetic and an electric field modulation method. The crossing-field strengths are in good agreement with the calculated values.     

Transport cross sections for charged particle scattering in (dense-) cesium plasma; electrical conductivity

Transport cross sections for the electron-ion and electron-electron scattering in (dense) cesium plasmas is determined with the partial wave method. The scattering phase shifts δ_l(k) are calculated numerically by means of the usual Numerov method and the advantageous amplitude — phase method for energies E = 10^-4··· 5 ryd and for Debye screening lengths R_D = (10···10³)a₀. Besides the usual Debye potential, also a Thomas-Fermi potential is applied for the cesium electron-ion interaction. The resulting transport cross sections are compared with the Born and quasi-classical approximations. Furthermore, the electrical conductivity of fully ionized cesium plasmas is determined and compared with respective Spitzer results.     

Optical delay with spectral hole burning in Doppler-broadened cesium vapor

The full frequency dependence of the optical delay in the Cs D₁ (6 ²S_1/2 ? 6 ²P_1/2) line has been observed, including all four hyperfine split components. Pulse delays of 1.6 ns to 24.1 ns are obtained by scanning across the hyperfine splitting associated with the lower ²S_1/2 state. Optical control of pulse delays in cesium vapor was demonstrated by pumping the D₂ (6 ²S_1/2 ? 6 ²P_3/2) transition and observing resulting holes in the D₁ delay spectrum. For a pump at four times the saturation intensity, the pulse delays are reduced by a maximum of 78% in a narrow region of 110 MHz. The frequency dependence of the delays of the probe laser in the vicinity of the spectral holes agrees with a Kramers–Kronig model prediction.     

A rubidium-stabilized ring-cavity resonator for optical frequency metrology: precise measurement of the D1 line in 133Cs

We have developed a ring-cavity resonator that can be used to measure the absolute frequencies of optical transitions with an uncertainty below 40 kHz. The length of the resonator is calibrated against a reference laser locked to the D₂ line of ⁸⁷Rb, the frequency of which is known with 6 kHz accuracy. We demonstrate the power of this technique by measuring the absolute frequencies of various hyperfine transitions in the D₁ line of ¹³³Cs. Our results agree with earlier measurements using the frequency-comb technique, and have similar accuracy. Measurement of the D₁-line frequency could lead to a more precise determination of the fine-structure constant. We also report a precise value of A=291.918(8) MHz for the hyperfine constant in the 6P_1/2 state.     

Hyperfine-structure investigation in the 6s5d configuration of135Ba and137Ba

The hyperfine structure of the metastable states of the 6s5d configuration of¹³⁵Ba and¹³⁷Ba has been studied by the atomic-beam magnetic resonance (ABMR) method. The metastable barium states were populated in a plasma-discharge inside the atomic-beam oven. The atoms emerging from the ABMR-apparatus were detected by the use of a dyelaser. Compared to conventional methods this technique has the advantage of being state selective. The following magnetic dipole and electric quadrupole interaction constantsa andb have been obtained:¹³⁷Ba:a(³ D ₁)=?520.536 (3) MHzb(³ D ₁)=17.890 (3) MHza(³D₂=415.928 (3) MHzb(³D₂)=25.899 (13) MHza(³D₃)=456.559 (4) MHzb ³D₃=47.390 (16) MHz¹³⁵Ba:a ³ D ₁=?465.166 (4) MHzb(³D₁)=11.642 (4) MHza(³D₂)=371.736(4) MHzb ³ D ₂=16.745 (14) MHza(³D₃)=408.038 (6) MHzb(³D₃)=30.801 (24) MHz Using these constants and the earlier known ones for the¹ D ₂ state the hyperfine structure for the 6s5d configuration has been analyzed with an effective hyperfine hamiltonian. Hyperfine parameters obtained from the analysis have been compared with theoretical values calculated with relativistic self-consistent-field (SCF) wavefunctions. The quadrupole moments have been evaluated with the following result Q(¹³⁵Ba) =0.20(3)b and Q(¹³⁷Ba) = 0.34(4)b uncorrected for the quadrupole shielding.     

Orientation of Cs 6p 2P3/2 atomic photofragments in a magnetic field: interference in the photodissociation of diatomic molecules

In a magnetic field, Cs₂ molecules were excited from the ground X¹Σ⁺_g(v_X=0,J_X=55) level to the D ¹Σ⁺_u(v=46,J=54) level by dissociation laser light linearly polarized parallel to the field, for which the magnetic sublevels were degenerated and thus all the transitions between them were simultaneously stimulated. Probe laser light excited the dissociated Cs 6p²P_3/2 atomic fragments to 6p²D_3/2 level and the resultant 6p²P_1/2 - 6d²D_3/2 emission was detected as the function of the wavelength of the probe light. The populations of the 6p²P_3/2,mj magnetic sublevels were determined from the relative strengths of the 6p²P_3/2,mj - 6d²D_3/2,m'j transitions induced by the probe light. Non-zero orientation O₀ was found in the ensemble of dissociated Cs 6p²P_3/2 atomic fragments. The orientation O₀ increased as the magnetic field strength increased. It was demonstrated both experimentally and theoretically that the orientation O₀ was induced through the interference in the excitation and dissociation paths in the presence of an external magnetic field, even when all degenerated transitions between the magnetic sublevels of the molecules are simultaneously excited by the light linearly polarized parallel to the field.     

Energies and chemical shifts of the sulphur 1s level and the KL2L3(1D2) Auger line in H2S,SO2 and SF6

The sulphur 1s binding energies and KL₂L₃(¹D₂) Auger energies have been measured in gaseous H₂S, SO₂ and SF₆. The experimental data, including the chemical shifts, are compared with various theoretical ab initio results. Theoretical and experimental values agree within 1-2 eV for the chemical shift and the binding energy of the 1s level, provided in the latter case relaxation, relativistic and correlation corrections are applied. Likewise, Shirley's method²⁰, which uses empirical energies, predicts the Auger energies satisfactorily. The measured S 1s binding energies are 2478.5(1) eV, 2483.7(1) eV and 2490.1(1) eV, and KL₂L₃(¹D₂) Auger energies are 2098.7(1) eV, 2095.5(2) eV, 2092.6(1) eV for H₂S, SO₂ and SF₆, respectively. The chemical shift for the 1s electron is found to be greater than for the 2s or 2p electron and in better accord with the prediction of the potential model. Data suggest the molecular relaxation energy to be small compared with the atomic relaxation energy.     

Collision broadening of spectral lines corresponding to transitions between excited levels of the cesium atom

The constants of pressure self-broadening of cesium have been measured for the transitions 6P _1/2−8D _3/2, 6P _3/2−10S _1/2, and 5D _5/2−nF(n=14−19). The constants of the resonance broadening of the 6P _1/2 and 6P _3/2 cesium levels, the constants of electron collisional broadening of thenF levels at a temperature ofT≈1500 K, and the oscillator strengths of the 5D _5/2−nF(n=14−18) transitions have been determined. Translated from Trudy Fizicheskogo Instituta im. P. N. Lebedeva, Lebedev Physics Institute, Russian Academy of Sciences, Moscow, Vol. 195, pp. 217–233, 1989.     

Polarisierte Anregung der metastabilen 6s 5d-Terme im Ba I-Spektrum und Messung derg J-Faktoren

In an atomic beam experiment Ba-atoms were excited in the metastable levels of the 6s 5d-configuration by optical pumping and electron impact. The three states 6s 5d ¹ D ₂ and³ D _1,2 were populated by optical excitation of the 6s 6p ¹ P ₁- and³ P ₁-level resp., which decay partly into the metastable states. The¹ D ₂- and³ D ₃-level could be excited and aligned by impact of 50 eV-electrons. Radiofrequency transitions between Zeemansublevels were detected by resonance scattering of light and theg _J-values of the four 6s 5d-levels were measured:g _J(^1D ₂)=1.0032 (2),g _J(^3D ₁)=0.4986 (2),g _J(^3D ₂)=1.1638 (2) andg _J(^3D ₃)=1.3341 (2).     

199Hg+光频标的黑体辐射频移

光学频率标准会受到环境温度的黑体辐射影响发生频移,进而影响其准确度. 本文估算了¹⁹⁹Hg⁺的超精细能级5d¹⁰6s²S_1/2 (F=0)和5d⁹6s^{2 2}D_5/2 (F=2)的极化率,得到了室温(300 K)下黑体辐射引起的相对频移为-5.4×10^-17, 最后讨论了低温环境下黑体辐射对¹⁹⁹Hg⁺光频标的影响.     

Collisional Broadening of CO<Subscript>2</Subscript> Transition Lines 10<Superscript>0</Superscript>0–00<Superscript>0</Superscript>1 by Inert Gas Atoms at 300–700 K

The spectrum of excitation of Rydberg states of thallium atoms has been investigated using a collimated atomic beam in a two-step isotope selective laser scheme 6²P_1/2 → 6²D_3/2 → Tl** in the presence of an electric field with a strength of up to 1.5 kV/cm near the level 16F_5/2. The optical transitions 6D_3/2 → 18D_3/2 and 6D_3/2 → 16G_7/2, which were induced by an external electric field and dipole-forbidden, have been studied experimentally. The values for the scalar polarizabilities (in units сm^–1/(kV/сm)²) α₀(16F_5/2) = 3.71 ± 0.3, α₀(18D_3/2) = 11.70 ± 0.25, and α₀(16G_7/2) = 44.1 ± 0.9, which are compared with the calculated one, have been obtained. The new values of energy parameters for the states 18D_3/2 and 16G_7/2 have been determined.