“原子物理学”课程思政建设的实现路径探究

“原子物理学”是高校物理学类专业的本科基础课程。该课程知识点丰富、人文精神底蕴深厚,具有很强的育人功能,是开展物理学课程思政建设的优势课程。通过深入挖掘“原子物理学”知识体系中所蕴含的思政元素,在教学过程中优化课程设计,潜移默化地将课程部分章节内容进行拓展,适时适度地将创新思维、科学家精神、责任与担当意识等融入课程体系与知识传授,可以实现专业课程的思想政治教育。

超冷铯分子0_u^+(6P_(3/2))长程态的高灵敏光缔合光谱研究

利用发展的调制俘获损耗荧光光谱技术实验测量了超冷铯分子0+u(6P3/2)长程态的高灵敏光缔合光谱.光谱探测范围较国际已有报道扩大了60 cm-1,观察到25个长程区域新的振动能级.通过Le Roy-Bernstein公式对振动束缚能数据进行拟合,获得了超冷铯分子0+u(6P3/2)态的长程系数C3为16.103±0.010.构建了超冷铯分子0+u(6P3/2)态长程区域的势能曲线.

磁光阱中超冷钠-铯原子碰撞的实验研究

研究了磁光阱中异核超冷钠铯原子的碰撞机理,测量了超冷钠原子的碰撞损失率,得到了钠-铯原子的碰撞损失系数β_(Na-Cs)与钠原子俘获光强度之间的关系.利用多普勒模型计算了不同俘获光强度下的钠原子磁光阱的阱深,得到了临界光强的理论值,与实验结果符合得较好.

利用双光缔合光谱技术直接测量超冷铯分子0_u^+(6S_(1/2)+6P_(1/2))长程态的转动常数的实验研究

实验获得了超冷铯分子6S1/2+6P1/2离解限下0+u长程态振动能级v=187的转动常数.首先利用调制的荧光光谱技术获得了高分辨的转动量子数J=0—6的超冷铯分子纯转动光谱.利用双光缔合光谱技术,构建了高精度的频率参考信号,进而得到了相邻转动能级间的频率间隔.最后通过非刚性转子模型拟合得到了转动常数和离心畸变常数.

基于磁悬浮大体积交叉光学偶极阱的Dimple光阱装载研究

三维拉曼边带冷却后的铯原子样品装载于一个磁悬浮的大体积交叉光学偶极阱中,继续加载一个小体积的光学偶极阱后,实现了Dimple光学偶极阱对铯原子的高效装载.对不同磁场下磁悬浮大体积光阱的有效装载势能进行理论分析与实验测量,得出最优化的梯度磁场和均匀偏置磁场,获得了基于磁悬浮大体积光阱的Dimple光学偶极阱的装载势能曲线,实现了Dimple光学偶极阱对经拉曼边带冷却后俘获在磁悬浮的大体积光阱中的铯原子样品的有效装载.比较了Dimple光学偶极阱分别从拉曼边带冷却、大体积的交叉光阱和消除反俘获势后的磁悬浮大体积光阱装载的结果,将俘获在磁悬浮大体积光阱中的铯原子样品装载到Dimple光学偶极阱,铯原子样品的密度提高了约15倍.

Efficient loading of cesium atoms in a magnetic levitated dimple trap

We report a detailed study of magnetically levitated loading of ultracold ^(133)Cs atoms in a dimple trap.The atomic sample was produced in a combined red-detuned optical dipole trap and dimple trap formed by two small waist beams crossing a horizontal plane.The magnetic levitation for the ^(133)Cs atoms forms an effective potential for a large number of atoms in a high spatial density.Dependence of the number of atoms loaded and trapped in the dimple trap on the magnetic field gradient and bias field is in good agreement with the theoretical analysis.This method has been widely used to obtain the Bose–Einstein condensation atoms for many atomic species.

Precise measurement of the line width of the photoassociation spectra of ultracold molecules by using a frequency shifter

We propose a technique to precisely measure the line width of the photoassociation spectra of the excited cesium molecule by using a frequency shifter to generate two laser beams with a precise frequency difference. A series of photoassociation （PA） spectra are recorded with two laser beam induced molecular lines, whose peak separation serves as an accurate frequency ruler to measure the line width of the PA spectra. The full width half maximum line width was studied as a function of PA laser intensity. The extrapolated value at zero laser intensity is （34.8± 0.22） MHz. By analyzing other broadening mechanisms, a value of （32.02 ± 0.70） MHz was deduced. It is shown that this scheme is inexpensive, simple, robust, and is promising for applications in a variety of other atomic species.

Effect of external magnetic field on the shift of resonant frequency in photoassociation of ultracold Cs atoms

We study the influence of external magnetic field on the shift of the resonant frequency in the photoassociation of ultracold Cs atoms, which are captured in a magnetically levitated optical crossed dipole trap. With the increase of the photoassociation laser intensity, the linear variation of the frequency shift is measured by recording the photoassociation spectra of the long-range 0_u^+ state of Cs molecule below the 6S_(1/2)+ 6P_(1/2) dissociation limit at different magnetic fields.The slope of the frequency shift to the intensity of the photoassociation laser exhibits a strong dependence on the external magnetic field. The experimental data is simulated with an analytic theory model, in which a single channel rectangular potential with the tunable well depth is introduced to acquire the influence of the magnetic field on the atomic behavior in the effective range where photoassociation occurs.

Arbitrary frequency stabilization of a diode laser based on visual Labview PID VI and sound card output

We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers.

Enhanced optical molasses cooling for Cs atoms with largely detuned cooling lasers

We report a detailed study of the enhanced optical molasses cooling of Cs atoms,whose large hyperfine structure allows to use the largely red-detuned cooling lasers.We find that the combination of a large frequency detuning of about-110 MHz for the cooling laser and a suitable control for the powers of the cooling and repumping lasers allows to reach a cold temperature of^5.5μK.We obtain 5.1×10^7 atoms with the number density around 1×10^12 cm^-3.Our result gains a lower temperature than that got in other experiments,in which the cold Cs atoms with the temperature of^10μK have been achieved by the optical molasses cooling.

Highly sensitive photoassociation spectroscopy of ultracold 23Na133Cs molecular long-range states below the 3S1/2＋6P3/2 limit

We present high resolution photoassociation spectroscopy of ultracold 23Na133Cs molecules in a long-range c3∑＋ state below the （3S1/2 ＋ 6P3/2） asymptote. We perform photoassociation spectroscopy in a dual-species magneto-optical trap （MOT） and detect the photoassociation resonances using trap-loss spectroscopy. By fitting the experimental data with the semi-classical LeRoy-Bernstein formula, we deduce the long-range molecular coefficient C6 and derive the empirical potential energy curve in the long-range region.

Enhancement of signal-to-noise ratio of ultracold polar NaCs molecular spectra by phase locking detection

We report a method of high-sensitively detecting the weak signal in photoassociation （PA） spectra of ultracold NaCs molecules by phase sensitive-demodulated trap-loss spectra of Na atoms from a photomultiplier tube. We find that the signal-to-noise ratio （SNR） of the PA spectra is strongly dependent on the integration time and the sensitivity of the lock-in amplifier, and our results show reasonable agreement with the theoretical analyses of the SNR with the demodulation parameters. Meanwhile, we investigate the effect of the interaction time of the PA laser with the colliding Na-Cs atom pairs on the SNR of the PA spectra. The atom loss rate is dependent on both the PA-induced atom loss and the loading of the MOT. The high-sensitive detection of the excited ultracold NaCs molecules lays a solid foundation for further study of the formation and application of ultracold NaCs molecules.

High-resolution photoassociation spectroscopy of ultracold Cs_2 long-range 0_g~- state: The external well potential depth

High-resolution photoassociation spectroscopy is reported using a modulation spectroscopy technology in a cesium atomic magneto-optical trap. The two lowest vibrational levels have been experimentally observed which have been theo- retically predicted in [Phys. Rev. A 75 052501 （2007）]. A new potential curve is obtained by using the Rydberg-Klein-Ress method with a well depth of -82,384 ＋ 0,026 cm-1, which is deeper than the result of previous experiment （-77.909 cm-1） and the theoretical prediction （-81.6445 cm- l ）.

Reanalysis of the photoassociation spectrum of ^(133)Cs_2 (6P_(3/2)) 1_g state

Reanalysis of the photoassociation spectrum of the weakly binding （6S1/2 ＋ 6P3/2） lg 133Cs2 levels, reported in the previous study [J. Mol. Spectro. 255 （2009） 106], is performed by using a Lu-Fano graph coupled to the improved LeRoy- Bernstein formula including two additional modified terms. A more accurate coefficient （c3） is obtained for the leading long-range potential （-c3/R3） of a diatomic molecule.

High resolution photoassociation spectra of an ultracold Cs_2 long-range 0_u^+ (6S_(1/2)+6P_(1/2) ) state

In this paper, ultracold cesium molecules are formed through photoassociation technology, which is carried out in a magneto-optical trap. High resolution photoassociaion spectra with the rotational progressions up to J = 7 are obtained. Three rovibrational levels of the long-range 0＋ state of Cs2 below the （6S1/2 ＋ 6P1/2） dissociation limit are specifically investigated. By fitting their binding energy intervals to the non-rigid rotational model, the rotational constant of the long- range 0u＋ state is determined. A proportional dependence of the value of the rotational constant on the vibrational quantum number is demonstrated.

Superfluid to Mott-insulator transition in a one-dimensional optical lattice

Bose–Einstein condensates(BEC)of sodium atoms are transferred into one-dimensional(1D)optical lattice potentials,formed by two laser beams with a wavelength of 1064 nm,in a shallow optical trap.The phase coherence of the condensate in the lattice potential is studied by changing the lattice depth.A qualitative change in behavior of the BEC is observed at a lattice depth of~13.7Er,where the quantum gas undergoes a transition from a superfluid state to a state that lacks well-to-well phase coherence.

Excessive levitation for the efficient loading of large-volume optical dipole traps

We study the excessive levitation effect in the magnetically levitated loading process of ultracohl Cs atoms into a large-volume crossed optical dipole trap. We analyze the motion of atoms with a non-zero combined gravito-magnetic force during the loading, where the magnetically levitated force catches up with and surpasses the gravity. We present the theoretical variations of both acceleration and velocity with levitation time and magnetic field gradient. We measure the evolution of the number of trapped atoms with the excessive levitation time at different magnetic field gradients. The dependence of the number of atoms on the magnetic field gradient is also measured for different excessive levitation times. The theoretical analysis shows reasonable agreement with the experimental results. Our investigation illustrates that the excessive levitation can be used to reduce the heating effect of atoms in the magnetically levitated loading process, and to improve the loading rate of a large-volume optical dipole trap.

The laser-intensity dependence of the photoassociation spectrum of the ultracold Cs_2(6S_(1/2) + 6P_(1/2))0_u^+ long-range molecular state

The high-resolution photoassociation spectrum of the ultracold cesium molecular 0＋ state below the 6S1/2 ＋ 6PI/2 limit is presented in this paper. The saturation of the photoassociation scattering probability is observed from the depen dence of the trap-loss probability on the photoassociation laser intensity. The corresponding resonant line width is also demonstrated to increase linearly with increasing photoassociation laser intensity. Our experimental data have good con sistency with the theoretical saturation model of Bohn and Julienne [Bohn J L and Julienne P S 1999 Phys. Rev. A 60 1].

Dependence of loading time on control parameters in a standard vapour-oaded magneto-optical trap

Loading time is one of the most important dynamic characteristics of a magneto-optical trap. In this paper, we primarily report on a detailed experimental study of the effects of some magneto-optical trap control parameters on loading time, including the background vacuum pressure, the magnetic field gradient, and the intensities of trapping and repumping lasers. We compare the results with previous theoretical and experimental results, and give qualitative analysis. These experimental investigations offer some useful guidelines to coatrol the loading time of magneto-optical traps. The controllable loading time achieved is helpful to enhance the signal-to-noise ratio of photoassociation spectroscopy, which is remarkably improved from 7 to 28.6.

High efficient Raman sideband cooling and strong three-body recombination of atoms

We report a highly efficient three-dimensional degenerated Raman sideband cooling(3D dRSC)that enhances the loading of a magnetically levitated optical dipole trap,and observe the strong atom loss due to the three-body recombination.The 3D dRSC is implemented to obtain 5×10^(7)Cs atoms with the temperature of~480 nK.The cold temperature enables 1.8×10^(7)atoms loaded into a crossed dipole trap with an optimized excessive levitation magnetic gradient.Compared to the loading of atoms from a bare magneto-optical trap or the gray-molasses cooling,there is a significant increase in the number of atoms loaded into the optical dipole trap.We derive for the three-body recombination coefficient of L_(3)=7.73×10^(-25)cm^(6)/s by analyzing the strong atom loss at a large scattering length of 1418 Bohr radius,and discover the transition from the strong three-body loss to the dominant one-body loss.Our result indicates that the lifetime of atoms in the optical dipole trap is finally decided by the one-body loss after the initial strong three-body loss.