High resolution fluorescence spectroscopy by use of a CW dye laser

The hyperfine structure of the Na D₂-line was investigated in a fluorescence experiment involving a narrow band tunable dye laser and a highly collimated atomic beam. The observed linewidth was less than 16 MHz (natural line-width 10 MHz). All hyperfine components were resolved.     

Hyperfine splitting,isotope shift,and level energy of the 3S states of (6,7)Li

We study the 2S-3S transition of (6,7)Li by high-precision laser spectroscopy using two-photon Doppler-free excitation and photoionization detection. Interferometric cross referencing to metrologic Rb 3S-5D two-photon transitions allowed measurement of the transition isotope shift and hyperfine splitting in the 3S state with precision at the 30 kHz level. The results are IS=11 453.734(30) MHz, A(3S)(6Li)=35.263(15) MHz, and A(3S)(7Li)=93.106(11) MHz. Combined with recent theoretical work, the isotope shift yields a new value for the change in squared nuclear charge radii DeltaR(2)=0.47(5) fm(2). This is compared with other work and some existing discrepancies are resolved.     

EPR and HYSCORE investigation of the electronic structure of the model complex Mn(imidazole)6: exploring Mn(II)-imidazole binding using single crystals

The electronic structure of the Mn(II)-imidazole binding was studied by EPR spectroscopy using the model complex Mn(Im)(6) diluted in a single crystal of Zn(Im)(6)Cl(2).4(H(2)O). The second rank zero-field splitting (ZFS) tensor (D tensor) of the two sites, a and b, present in the crystal was determined by measuring the orientation patterns of the echo-detected EPR spectra in three different planes at 10K (D(a)=-106, D(b)=-118, E(a)=-17, E(b)=-22x10(-4)cm(-1). Euler angles with respect to the crystal habitus: alpha(a)=13 degrees , beta(a)=76 degrees , gamma(a)=108.5 degrees , alpha(b)=14 degrees , beta(b)=73.5 degrees , gamma(b)=103.5 degrees ). The contribution of cubic ZFS terms to the spectrum allowed us to determine the orientation of the N-Mn-N directions of the complex as well (Euler angles in the D tensor reference frame alpha=100 degrees , beta=23 degrees , gamma=0 degrees , both centers having the same orientation). The hyperfine interactions with (14)N were explored by HYSCORE spectroscopy. The correlation patterns and modulation amplitudes in the 2D experiments were studied for different electron spin transitions and orientations of the crystal. Signals of three different pairs of nitrogens were found. The results were analyzed considering that the N-Mn binding directions are principal directions of the hyperfine and nuclear quadrupole tensor of (14)N. All three pairs of nitrogens were found to be almost equivalent with an isotropic contribution of A(iso) approximately 3.2MHz and an almost axial anisotropic coupling of 2T approximately 1.1MHz along the N-Mn bonding direction. The nuclear quadrupole principal values are 1.5MHz along the bonding direction, -0.6MHz in the direction perpendicular to the imidazole plane, and -0.9MHz in the direction perpendicular to both.     

Hyperfine Paschen-Back regime realized in Rb nanocell

A simple and efficient scheme based on a one-dimensional nanometric-thin cell filled with Rb and strong permanent ring magnets allows direct observation of the hyperfine Paschen-Back regime on the D(1) line in the 0.5-0.7 T magnetic field. Experimental results are perfectly consistent with the theory. In particular, with σ(+) laser excitation, the slopes of the B-field dependence of frequency shifts for all 10 individual transitions of (85,87)Rb are the same and equal to 18.6 MHz/mT. Possible applications for magnetometry with submicron spatial resolution and tunable atomic frequency references are discussed.     

Qubits based on spectrally selected groups of Pr<Superscript>3+</Superscript> ions in a LaF<Subscript>3</Subscript> crystal

Spectral selection, i.e., the separation of a group of particles with a spread in resonance frequencies smaller than the hyperfine splitting of working levels has been implemented by the method of burning of long-lived spectral dips in the inhomogeneously broadened absorption line of Pr³⁺ in a LaF₃ crystal. The possibility of implementing qubits (basic elements of quantum computations) on ensembles of spectrally selected particles and the main operations with them, including the manipulation of the populations of hyperfine (qubit) levels and the controlled shift of the absorption line of one spectrally selected group of ions upon excitation of another group (two-qubit operations), has been demonstrated. The decay rates of the population of hyperfine sublevels of the ground state of the spectrally selected group of particles have been measured.     

铯原子气室中D2线泵浦探测光谱的实验观测

在铯原子气室中采用偏振方向相互垂直且同向传播的线偏泵浦光和探测光，研究了铯原子D2线的泵浦探测光谱。由于在6 S1/2 F=3 – 6 P3/2 F’=2 超精细跃迁中存在多个L型塞曼子能级结构，从而产生了电磁诱导透明导致的吸收减弱；而在6 S1/2 F=4 – 6 P3/2 F’=5 超精细跃迁中则观测到了电磁诱导吸收。通过改变泵浦光的失谐量，在电磁诱导透明形成的吸收减弱凹陷和电磁诱导吸收产生的吸收增强峰内部均观察到了反常的吸收信号反转。     

基于探测器标准的高精度光谱辐射标准光源

本文在评述低温绝对辐射计和SIRCUS发展的基础上,讨论了基于探测器标准的光谱可调谐自校准标准光源的工作原理、发展与应用前景。在探测器型光谱辐射标准研究方面,工作在液氦温度的低温绝对辐射计不确定度达0.01%。美国国家标准与技术研究院(NIST)建立的均匀光源光谱辐照度和光谱辐亮度响应度定标装置(SIRCUS)采用一系列激光器,由低温绝对辐射计传递的硅陷阱探测器定标,不确定度已达到0.1%,成功应用于空间遥感仪器高精度辐射定标。分析认为,发展中的基于探测器标准的光谱可调谐自校准标准光源,定标精度高,自行校正老化、衰减,保证了定标精度长期稳定。     

Very narrow-bandwidth tunable infrared difference frequency generation with injection-locked dye lasers

Two flashlamp pumped dye lasers of very high spectral quality are mixed in a LiIO₃ crystal to generate a tunable infrared beam through the difference frequency mixing. Thanks to the injection-locking process of the pulsed dye lasers leading to a linewidth of 6 MHz with peak powers of about 10 kW, we obtain an IR beam tunable from 3.5 to 5.9 m with a peak power of 40 W and a linewidth of 9 MHz. As an application we present a spectrum of N₂O obtained by differential absorption near 1880 cm^–1. The lines of thisQ-branch are Doppler limited at the working pressure (10² Pa).     

法-珀干涉绝对距离测量中的声光移频器双通道配置方法

为在能量天平动圈位移测量中实现大范围纳米精度法-珀干涉绝对距离测量, 提出了声光移频器双通道配置, 实现了调谐范围为200 MHz的可调谐频差. 通过分析声光移频器调制带宽与衍射效率的平衡与入射光束聚焦透镜的关系, 确定透镜的最佳焦距范围; 利用零级光斑分布特点准确定位入射光束, 保证一级衍射光束质量. 声光移频器在调制带宽内的实验单通道和双通道峰值衍射效率分别为79.54%, 61.41%; 声光移频器双通道配置输出的一级衍射光束与入射本征光束的拍频范围为440-640 MHz, 是单通道调制带宽输出220-320 MHz的两倍, 信噪比好. 理论分析表明, 声光移频器双通道配置方法实现的可调谐频差可测量腔长变化范围约为53 mm的折叠法-珀腔.     

Ba原子6s5d~3 D与6p5d~3 F态的超精细结构及态间跃迁的同位素移动的直接确定

提出并演示了一种光泵预选态的原子光谱测量方法,并对Ba原子的6s5d3 D态与6p5d3 F态的超精细结构及该跃迁的同位素移动进行了直接测量。首先利用791nm的激光激发Ba原子特定同位素及特定超精细结构的6s6s 1 S0→6s6p3 P1跃迁,并利用6s6p3 P1→6s5d3 D2的自发辐射有选择地分别将这些同位素制备到6s5d3 D2态不同的超精细能级上,再用778nm的激光扫出对应的6s5d3 D2→6p5d3 F2跃迁的荧光光谱,通过这几组光谱之间的对比直接实现了对22条超精细谱线的认定和归属,从而得到了135 Ba和137 Ba的6s5d3 D2能级与6p5d3 F2能级的超精细结构常数及该跃迁的同位素移动。     

Realization of Optical Phase Locked Loop at 9.2GHz between Two Independent Diode Lasers

The optical-phase-locked-loop (OPLL) at 9.2GHz between two independent narrow linewidth diode lasers is realized. Ultrabroad servo bandwidth at 4MHz is first achieved and it is guaranteed that the full spectral characteristics of the master laser can be transferred to the slave laser. The experimental results prove that the coherence between two lasers is about 99%. This offers a new method to study the interaction between lasers and atoms based on the ground hyperfine structure of caesium atoms.     

High-efficiency single-mode dye layer

Stable single-mode operation is obtained in a longitudinally pumped grazing-incidence tunable dye laser. Only a grating is used as a selective element in a very short cavity, producing 580 ± 50MHz spectral width. The proposed laser configuration features reliability, simplicity and easiness of operation. The compact cavity allows short-pulse excitation and the longitudinal pump provides increased efficiency up to 15%.     

Precise frequency measurements of atomic transitions by use of a Rb-stabilized resonator

We demonstrate a technique for frequency measurements of atomic transitions with a precision of 30 kHz. The frequency is measured with a ring-cavity resonator whose length is calibrated against a reference laser locked to the D2 line of 87Rb, the frequency of which is known with 10-kHz accuracy. We have used this method to measure the hyperfine structure in the 5P(3/2) state of 85Rb. We obtain precise values for the hyperfine constants, A = 25.041(6) MHz and B = 26.013(25) MHz, and a value of 77.992(20) MHz for the isotope shift in the D2 line.     

High-resolution rotational spectroscopy in a cold ion trap: H2D+ and D2H+

The lowest-lying 1(01) <-- 0(00) transition of para-H(2)D(+) and 1(11) <-- 0(00) of ortho-D(2)H(+) has been detected by the enhancement of the D/H isotope exchange reaction in collisions with p-H2 upon rotational excitation. These are the first pure rotational spectra of molecular ions by action spectroscopy. For this purpose, a cryogenic multipole ion trap has been combined with narrow-band tunable radiation sources operating in the 1.25 to 1.53 THz range. The low temperature of the ions allows us to determine the astronomically important transitions with a relative precision of Delta nu/nu=10(-8). While the 1 476 605.708(15) MHz line center frequency for the o-D(2)H(+) transition agrees very well with previous unpublished work, the 1 370 084.880(20) MHz line center frequency for the p-H(2)D(+) transition deviates by 61 MHz. Potential future applications of this new approach to rotational spectroscopy are discussed.     

High-resolution spectroscopy with and frequency stabilization of a cw dye laser

The hyperfine splittings of the Na D₁ and D₂ lines were investigated using a single mode cw dye laser. The light of the laser was scattered by the atoms of an atomic beam and the fluorescent light was observed as the frequency of the laser was tuned across the D lines. The Doppler width of the atomic beam was reduced to about 2.5 MHz so that the absorption width of the atoms of the beam was essentially determined by the natural width of the 3²P_1/2 and 3²P_3/2 levels, which is about 10 MHz. Since the linewidth observed for the hyperfine transitions was 30 MHz, most of the hyperfine components of the D₁ and D₂ lines could be resolved. In another experiment the frequency of the dye laser was locked to a hyperfine transition of the D₁ line. The observed variation of the output frequency of the dye laser was less than ±1.5 MHz. In addition, the intensity of the dye laser was controlled to about 10⁻³, using an electro-optically variable transmission filter.     

Hyperfine structure measurements in the ground states4 F 3/2,4 F 5/2 and4 F 7/2 of Ta181 with the atomic beam magnetic resonance method

Applying a recently developed evaporation technique for refractory elements the following results have been obtained for Ta¹⁸¹ in an atomic beam magnetic resonance experiment studying the hyperfine structure of 3 levels of the ground state multiplet⁴ F: $$\begin{gathered} g_J (^4 F_{3/2} ) = 0.45024 (4) \hfill \\ \Delta v (^4 F_{3/2} ;F = 5 \leftrightarrow F = 4) = 1822.389 (6) MHz \hfill \\ \Delta v (^4 F_{3/2} ;F = 4 \leftrightarrow F = 3) = 2325.537 (2) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 6 \leftrightarrow F = 5) = 1451.476 (7) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 5 \leftrightarrow F = 4) = 1537.530 (8) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 4 \leftrightarrow F = 3) = 1444.685 (2) MHz \hfill \\ \Delta v (^4 F_{7/2} ;F = 4 \leftrightarrow F = 3) = 1218.372 (2) MHz. \hfill \\ \end{gathered}$$ From these measurements the following constants of the magnetic dipole interaction (A) and the electric quadrupole interaction (B) have been derived: $$\begin{gathered} A (^4 F_{3/2} ) = 509.0801 (8) MHz \hfill \\ B (^4 F_{3/2} ) = - 1012.251 (8) MHz \hfill \\ A (^4 F_{5/2} ) = 313.4681 (8) MHz \hfill \\ B (^4 F_{5/2} ) = - 834.820 (12) MHz. \hfill \\ \end{gathered}$$      

2D-REFINE spectroscopy: separation of overlapping hyperfine spectra

We show on a mixture of three spectrally overlapping paramagnetic compounds TEMPO, BDPA and CuHis that it is possible to separate their field-swept and hyperfine spectra based on the difference in their longitudinal relaxation times T1. This was achieved in a two-dimensional experiment, where one dimension corresponds to the spectral domain and the second dimension encodes the relaxation behavior of the individual compound. Inverse Laplace Transform with respect to this domain separates the field-swept and hyperfine spectra of the individual compounds in the relaxation rate domain. This extends our formerly proposed Relaxation Filtered Hyperfine (REFINE) method to be applicable to more than two spectrally overlapping spectra by adding a further dimension to the chosen EPR experiment.     

522 W average power, spectrally beam-combined fiber laser with near-diffraction-limited beam quality

We report a three-channel, spectrally beam-combined (SBC), 1 mum fiber laser that produces 522 W of average power with near-diffraction-limited (M2 ~ 1.2) beam quality. The laser features a SBC power combining efficiency of 93%, versatile master-oscillator, power-amplifier fiber channels with up to 260 W of narrow-band, polarized, and near-diffraction-limited output that is tunable over nearly the entire 1 micro m Yb(3+) gain bandwidth, and excellent prospects for significant power scaling. To our knowledge, these results represent the highest beam quality and average power achieved to date for a beam-combined fiber laser system.     

Room-temperature spectral hole burning in an engineered inhomogeneously broadened resonance

We observe spectral hole burning in a room-temperature optical fiber pumped by a spectrally broadened pump beam. This beam drives the stimulated Brillouin process, creating an inhomogeneously broadened resonance in the material whose shape can be engineered by tailoring the beam's spectrum. A monochromatic saturating beam "burns" a narrow spectral hole that is approximately 10(4) times narrower than the inhomogeneous width of the resonance. This research paves the way toward agile optical information processing and storage using standard telecommunication components.     

High-resolution diode-laser spectroscopy on a fast beam of metastable atoms for detecting very rare krypton isotopes

A fast krypton ion beam with an energy of 10 keV is transferred through a mass filter and neutralized in a Rb- (or Cs-) vapour charge exchange cell. The emerging beam of metastable Kr atoms of a selected Kr isotope is collinearly irradiated with a tunable cw GaAlAs diode laser at 811 nm. The spectrum of the 1s ₅–2p ₉ transition covers 10 GHz and consists of one line each for the five stable isotopes of Kr with even mass number and 15 hyperfine structure lines of⁸³Kr. The individual lines are recorded by detecting the fluorescence signal perpendicular to the beams. Photons are guided to the PM tube by diffuse reflection from a high reflectance thermoplastics light collector. Up to 20 photons per atom are emitted by cycling between the two states during the flight time of 1.2 µs through the detector. The observed absorption linewidth of 100 MHz is a combination of laser linewidth and energy uncertainty in the fast atomic beam. In order to achieve maximum isotope selectivity the beam energy has to be adjusted in such a way that the Doppler shifted lines of all isotopes form an optimum pattern for detecting the very rare isotopes⁸¹Kr and⁸⁵Kr in natural environmental samples.