Two-color polarization spectroscopy of rubidium

We report on two-color, two-photon polarization spectroscopy in a room-temperature rubidium vapor. We use two separate lasers, a strong pump at 780 nm to induce an anisotropy in the atomic polarization and a weak probe at 776 nm to interrogate this anisotropy. The lasers are resonant with the 5²S_1/2 → 5²P_3/2 and 5²P_3/2 → 5²D_5/2 transitions in rubidium, respectively. Finally, we have used our polarization spectroscopy signal as an error signal to lock the 776 nm laser. This modulation-free locking scheme allows us to detune the lock point of the second laser by adjusting the detuning of the laser used for the first transition.     

Optimization of polarization spectroscopy for rubidium D lines

Polarization spectroscopy of the D lines of rubidium atoms is investigated experimentally,especially with different pump powers and cell temperatures.We find that there are four candidate transitions suitable for frequency stabilization,and optimal pump powers and cell temperatures are also presented to obtain a perfect signal with maximal amplitude and slope.The optimal signal is insensitive to the fluctuations of laser power and the temperature,which can enhance the performance of frequency locking.     

Self-rotation of optical polarization in rubidium vapor

We present an experimental and theoretical study of self-rotation of optical polarization in a rubidium vapor.The atomic vapor is placed in a magnetic shielding cavity to suppress the Faraday rotation effect.In our experiment,Doppler-free spectroscopy configuration is used,and F = 2 → F ’ = 3 transition of 87Rb D2 line is chosen.We observe self-rotation of optical polarization effect at different pump light ellipticities.A theoretical analysis is then provided based on the experimental conditions.Theoretical simulation and experimental results are in good agreement.     

铷原子蒸汽中的光偏振旋转效应

对铷原子(⁸⁷Rb)蒸汽中的法拉第旋转、光学偏振自旋转以及二者的叠加旋转效应进行了理论和实验研究.对三种情况下旋转现象建立了简单而有效的理论模型. 实验中把铷原子泡置于自行设计的磁屏蔽腔内, 以屏蔽地磁场的影响.实验选择⁸⁷Rb F=2→F'=3能级D2跃迁线并采用零多普勒光谱 实验结构消除多普勒展宽对实验光谱的影响. 实验中分别观测到了三种旋转现象,实验结果与理论模拟结果非常符合.     

Nonexponential decay of spin polarization in rubidium vapor

Experimental data on the decay of spin polarization in rubidium vapor are compared with inferences of the theory developed by the authors for spin-polarized Boltzmann gases. It is demonstrated that the nonexponential pattern of polarization decay points to the anisotropy of the indicatrix of inelastic scattering of rubidium atoms at high temperatures. Estimates are obtained of the degree of anisotropy of such inelastic scattering, i.e., scattering with variation of total spin. Under the experimental conditions, the indicatrix of inelastic scattering turns out to be highly extended forward, with the degree of anisotropy of the order of 1000.     

Microwave spectroscopy of cold rubidium atoms

The effect of microwave radiation on the resonance fluorescence of a cloud of cold ⁸⁵Rb atoms in a magnetooptical trap is studied. The radiation frequency was tuned near the hyperfine splitting frequency of rubidium atoms in the 5S ground state. The microwave field induced magnetic dipole transitions between the magnetic sublevels of the 5S (F=2) and 5S (F=3) states, resulting in a change in the fluorescence signal. The resonance fluorescence spectra were recorded by tuning the microwave radiation frequency. The observed spectra were found to be substantially dependent on the transition under study and the frequency of a repump laser used in the cooling scheme.     

Repetition rate spectroscopy of the dark line resonance in rubidium

Spectroscopy of a Λ structure in ⁸⁷Rb is performed with a mode locked laser. A dark line, resulting from population trapping between the hyperfine levels, is observed when the repetition rate is 1/57th of the hyperfine splitting. Simulation of coherent interaction of Rb atoms with laser pulses shows darklines corresponding to different submultiple of the hyperfine splitting. It is demonstrated experimentally and theoretically that the resonance width is insensitive to fluctuations in optical frequency.     

Doppler spectroscopy of arbitrarily polarized light in rubidium

We present an experimental and theoretical study of the transmission of an arbitrarily polarized laser beam for a Doppler broadened rubidium vapor cell. As the polarization of the probe beam was varied from linear to circular, the transmission for the transitions F_g = 3 → F_e = 2, 3, 4 of the D₂ line of ⁸⁵Rb atoms was measured and compared with calculated results. In the calculation, the time-dependent absorption coefficient, calculated numerically from the density-matrix equation, was averaged over the velocity distribution and various transit time crossing the laser beam. The final transmission was obtained by considering the Gaussian profile of the laser beam. We found good agreement between experimental and calculated results.     

Magnetic field modulation spectroscopy of rubidium atoms

The magnetically modulated saturation absorption profile is studied for a wide range of external DC magnetic field. The salient features of Doppler-free signal generated by laser frequency modulation and atomic energy level modulation are compared. The DC offset of the signal profile is found to be unstable as the external DC magnetic field is changed. The technical difficulty of tuning laser frequency under locked condition over a large frequency span is discussed along with possible solutions.     

Analytic calculation of feynman amplitudes

A new method is proposed for calculating amplitudes of processes involving spin-1/2 fermions. The method is based on the use of the isotropic-vierbein vectors in Minkowski space and the basis spinors associated with them. The amplitudes for the electron-positron interaction processes e^?e⁺ → ff and e^?e⁺ → W^?W⁺ and the amplitude for one of the possible diagrams for the process e⁺e^? → e⁺e^?e⁺e^?e⁺e^? are calculated in order to test and illustrate the potential of the method.     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法。基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况。通过与文献结果的比较,验证了本文计算方法和结论的可靠性。     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法 .基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况.通过与文献结果的比较,验证了本文计算方法和结论的可靠性.     

Analytic calculation of field-strength correlators

Field correlators are expressed using background-field formalism through the gluelump Green’s functions. The latter are obtained in the path-integral and Hamiltonian formalism. As a result, the behavior of field correlators is obtained at small and large distances for both perturbative and nonperturbative parts. The latter decay exponentially at large distances and are finite at x = 0, in agreement with OPE and lattice data. The text was submitted by the author in English.     

Improved measurement of polarization state in terahertz polarization spectroscopy

A calibration scheme is presented for improved polarization state measurement of terahertz pulses. In this scheme the polarization response of a two-contact terahertz photoconductive detector is accurately measured, and is used to correct for the impact of the nonidealities of the detector. Experimental results show excellent subdegree angular accuracy and at least 60% error reduction with this scheme.     

Exact calculation of the muon polarization function

The spin dynamics of a polarized muon at an interstitial lattice site interacting with four or six nearest neighbouring nuclear spins withJ=1/2 has been investigated. The difference from the results of the Kubo-Toyabe theory is pointed out. The interaction of a muon with four nuclei with spinJ=1 including both dipolar and quadrupolar effects is considered, and some numerical results are shown.     

铷原子气体自旋噪声谱的测量与改进

利用自主设计并制作的基于现场可编程门阵列的实时傅里叶变换采集卡(FFTsDAC),采用线偏振光检测碱金属铷原子气样品中的自旋随机涨落(即自旋噪声谱).详细讨论了背景噪声以及自旋噪声随探测光光强的变化关系,证实了自旋噪声来自于系统中自旋的随机涨落.对比了两种FFTsDAC(8 bit采样的FFTsDACl和12 bit采样的FFTsDAC2)的测量性能,分析了影响实验信噪比的因素.FFTsDAC2具有更高的测量效率和采样深度以及更长的单次采样时间,因而具有更高的信噪比和更好的频率分辨率,与数值模拟的结果一致.     

Zeeman effect in the polarization spectroscopy of Na

The Doppler-free polarization spectrum of the D₁ line has been studied in fields of about 50 G and in zero field. Although the principal Zeeman resonances are resolved, the signals are confusing because of the very large number of cross-over resonances. Cross-over resonances also seriously distort well-resolved resonances in zero field. An interpretation is given, based on combining a first-order theory of optical pumping with the theory of Faraday rotation and dischroism.