Frequency measurements on optically narrowed Rb-stabilised laser diodes at 780 nm and 795 nm

Laser diodes, optically narrowed using the technique of resonant optical feedback, have been frequency stabilised to hyperfine transitions of the two Rb D lines at 780 nm and 795 nm. The best frequency stability of the beat between two similar lasers was 1.5 kHz (4 parts in 10¹² of the optical frequency) observed for an averaging time of 10 s. A frequency reproducibility of 44 kHz (one standard deviation) was observed on strong isolated hyperfine components, and possible causes of frequency shift were investigated. Values for the Rb hyperfine intervals were obtained, leading to an improved determination of the excited state hyperfine constants of ⁸⁵Rb and ⁸⁷Rb, and the isotope shift. The absolute frequencies of the hyperfine transitions of the two D lines were determined interferometrically by comparison with an ¹²⁷I₂-stabilised He-Ne laser at 633 nm. Measurements were made on component c at 795 nm and the d/f level crossing at 780 nm. The frequencies were found to be 377106271.6 MHz and 384227981.9 MHz respectively under the chosen conditions, with an uncertainty of ±0.4 MHz, limited by knowledge of the reference frequency. These results represent the most accurate and complete characterisation to date of laser diodes stabilised to Doppler-free Rb spectra.     

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585 nm

The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in ¹²⁷I₂ are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a₁₅ and P(80)21-1 a₁₀ are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.     

Iodine stabilization of a diode laser in the optical communication band

The iodine molecule has frequently been used as a frequency reference from the green to the near-infrared wavelength region (500-900 nm). We describe the frequency locking of the second-harmonic signal of a 197.2-THz (1520.25-nm) distributed-feedback diode laser to the absorption lines of the iodine hyperfine structure; a frequency jitter below 0.1 MHz was achieved at a 300-ms time constant. This scheme provides a simple, compact, and high-performance frequency reference in the optical communication band.     

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.     

The hyperfine coupling tensors of muonated radicals in single‐crystal benzophenone

The hyperfine coupling tensors of muonated radicals in a large single crystal of benzophenone have been determined by measuring the hyperfine couplings of the radicals as the crystal was rotated about three orthogonal axes. Signals from four radicals were observed, corresponding to the four molecules per unit cell in the crystal. Due to an ambiguity in the data we are unable to discriminate between two similar hyperfine coupling tensors. Both lead to an isotropic hyperfine coupling of \sim32 MHz, contrasting with the solution value of 42 MHz obtained earlier in diethyl ether. The anisotropic components of the tensor are relatively large, at approximately -15 MHz, -6 MHz and 21 MHz, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Absolute frequency measurements of the 0002-0000, 2001-0000, and 1201-0000 bands of N2O by heterodyne spectroscopy

The absolute frequencies of 39 lines in the 00⁰2-00⁰0, 20⁰1-00⁰0, and 12⁰1-00⁰0 bands of N₂O in the range 4300–4800 cm^?1 have been measured by heterodyne frequency techniques. The lines were each measured in Doppler-limited absorption, with a color-center laser as a tunable probe of the N₂O and two stabilized CO₂ lasers as reference frequencies. New rovibrational constants have been fitted to these measurements. Tables of calculated transition frequencies are given, with estimated absolute uncertainties as small as 10^?4 cm^?1. The pressure shifts of four lines have been measured, and the values fall within the range of 0 to ?2 MHz/kPa (0 to ?0.2 MHz/Torr).     

Direct experimental evidence of the hyperfine predissociation of molecular iodine using a saturated absorption experiment

A saturated absorption technique using an actively stabilized C.W. dye laser has been used to study the hyperfine structure of some lines lying in the 9-3, 10-3, 11-3, 11-4, 12-3 bands of the B-X system of molecular iodine. The comparison of the different spectra shows that the intensities of the different hyperfine components of one line deviate from the 2F + 1 proportionality when 'v decreases towards the value 'v=6 where the potential curves of the ³Π⁺₀ and 1u states are crossing. The preliminary experimental results concerning the hyperfine component intensity variations versus the quantum numbers 'v, J and F give a direct qualitative support to the recently reported hyperfine predissociation in I₂.     

Pressure broadening by argon in the hyperfine resolved P(10) and P(70) (17,1) transitions of I2 XΣ(0g)→BΠ(0u) using sub-Doppler laser saturation spectroscopy

The dependence of pressure broadening upon hyperfine component in the P(10) and P(70) lines of the (17,1) band of the I₂ X¹Σ(0_g⁺)→B³Π(0_u⁺) has been studied using laser saturation spectroscopy. By limiting absorption to the zero velocity group, Doppler broadening is removed, lineshapes with widths (FWHM) <9 MHz are detectable, and collision-induced broadening is measured at pressures of 0.2-1.2 Torr. The rates for broadening by argon are 8.3±0.3 and 10.7±0.4 MHz/Torr for the P(70) and P(10) lines, respectively. No significant variation in broadening rates is observed for the 15 hyperfine components of these even rotational lines. The effects of velocity cross-relaxation introduce a broad baseline into the spectra, which is strongly dependent on rotational state, pressure, and laser modulation frequency. The observed broadening rates correlate well with prior measurements and the polarizability of the collision partner.     

铯原子7S1/2态磁偶极超精细常数的测量

在室温下的原子气室中, 基于铯原子6S_1/2-6P_3/2-7S_1/2(852.3 nm+1469.9 nm) 阶梯型能级系统, 利用电光调制器的主频和±1级边带分别产生的三套双共振吸收光谱, 当驱动电光调制器的信号源频率严格等于7S_1/2态超精细分裂的能级间隔时, 三套谱线中的一些超精细跃迁谱线重叠且线宽最窄, 利用这一现象很好地避免了激光器频率扫描时非线性效应的影响, 测量出了7S_1/2 态超精细分裂能级间隔: 2183.72 MHz±0.23 MHz, 并计算出该态的磁偶极超精细常数: A_hfs= 545.93 m MHz±0.06 MHz, 与文献中报道的测量结果一致.     

Jet-Cooled Optical Spectroscopy of FeN between 16 300 and 21 600 cm(-1)

We report the first gas-phase spectroscopic study of iron mononitride (FeN). FeN molecules were generated by the reaction of laser-ablated Fe atoms with NH(3) under supersonic jet-cooled conditions. Laser-induced fluorescence excitation spectra were measured between 16 300 and 21 600 cm(-1), and rotational analyses have been performed for about 25 vibronic bands. The Omega value of the ground state has been determined to be 52, which could be the spin-orbit component of (2)Delta (ellipsis 1delta(3)9varsigma(2)) or (4)Pi (ellipsis 1delta(3)9varsigma(1)4pi(1)). The excited states in the visible absorption region show very complicated rovibronic structures due to heavy perturbations. Excited state lifetimes, (56)Fe(14)N/(56)Fe(15)N isotope shifts, and dispersed fluorescence spectra were measured for the majority of the bands, which were classified into the five Omega = 52-XOmega = 52 band systems. Copyright 2000 Academic Press.     

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.     

~6Li原子跃迁频率和超精细分裂的精密测量

本文实现了可用于锂原子频率精密测量的冷原子系统,获得了大数目的原子样品;利用西西弗斯冷却和速度选择相干布居俘获实现了~6Li的冷原子的灰色黏胶冷却,原子的温度被冷却到多普勒冷却极限以下,达到50μK;利用光学频率梳,实验上测量了D1线的跃迁频率和超精细分裂,测量结果和理论计算相接近,可以和目前最精确的测量相比较.这些测量为进一步的轻质量原子频率的精密测量、α常数以及核半径的精确标定打下了基础.     

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.     

Pressure broadening of the NO2 hyperfine multiplet at 93 GHz

Line shapes of the hyperfine NO₂ 26(1,25)←25(2,24) rotational transition have been measured at pressures below 3 torr with a bridge spectrometer originally designed for direct absolute absorption studies. The multiplet consists of six lines with δF=δJ=δN=1 in the vicinity of 93,445 MHz. The same line-broadening parameter of 3.7 MHz/torr and the same maximum absorption of 1.8×10^-5 cm^-1 have been found for all 6 lines. The maximum absorption of the strongly overlapped multiplet at a pressure of 10 torr was measured to be 1.06×10^-4 cm^-1, in good agreement with the theoretical value. The interference effect of the overlapping lines turns out to be below ?10%, so that a simple superposition of lorentzian shapes is a good approximation for this case. The remaining difference can be compensated for by the introduction of an overlap parameter for each line.     

Fourier transform high-resolution measurements on the 2 ← 0, 3 ← 0, 4 ← 0, 5 ← 0 infrared absorption bands of HI and DI

Fourier absorption spectra of HI and DI were recorded simultaneously in a very large spectral range and the results enabled the prediction of the 1 ← 0 band of TI. For the wavenumbers of most lines, the absolute accuracy was estimated to be better than 2 × 10^?7 × σ. The TI spectrum was calculated with an estimated precision of 20 × 10^?3 cm^?1 by extrapolation from the HI and DI spectra through a Dunham analysis corrected for the Born-Oppenheimer approximation. In the course of this experiment, Doppler-limited electricquadrupole hyperfine structures were detected for low J lines of the first overtone bands.     

Theoretical assignment of the observed hyperfine structure in the saturated absorption spectra of I2129 and I127I129 vapors in the 633 nm wavelength region

The detailed structure observed in the saturated absorption spectrum of I₂¹²⁹ vapor in the 633 nm wavelength region in the spectral interval reported by Knox and Pao, has been interpreted to be the overlap between the hyperfine lines of the 8-4 P(54) line of I₂¹²⁹ and the 6-3 P(33) line of the I¹²⁷I¹²⁹ vapor. In this assignment, the nuclear electric quadrupole and nuclear magnetic terms in the Hamiltonian were diagonalized exactly and certain molecular parameters were varied to obtain the best fit with the observed spectrum. For I₂¹²⁹, the calculated distance (separation) of the center of the 8-4 P(54) line from the line center of the Ne²⁰ 633 nm laser transition is 0.04 cm^?1 and the RMS deviation between the theoretical and experimental hyperfine spectra is 0.3 MHz. Although the calculated frequency of R(60) transition in the 8-4 band is only 0.03 cm^?1 from the center of the laser line, we conclude on the basis of the larger RMS error (0.5 MHz) that this latter transition is less likely to be that responsible for the structure discussed in this paper.     

Spiro－Oxaziue染料掺杂高分子材料光致变色效应的研究

报道Ｓｐｉｒｏ－Ｏｘａｚｉｕｅ染料掺杂高分子（ＳＯ／ＰＶＡ）膜具有很强的可逆光致变色效应，通过对这种高分子膜吸收光谱的测试，证实ＳＯ分子具有二个特征吸收带，一个在３６０ｎｍ，另一个在５９５ｎｍ，分别对应于二个分子异构体ＳＯ１和ＳＯ２，有关这种ＳＯ／ＰＶＡ光致变色过程的研究给出了ＳＯ１对紫外光和ＳＯ２对可见光（波长在５１５ｎｍ）的吸收系数分别为１．２ｃｍ２／Ｊ和６×１０－２ｃｍ２／Ｊ，ＳＯ２的寿命为３８ｓ。最后本文给出了采用这种ＳＯ／ＰＶＡ膜实现紫外－可见光图像转换和空间光调制操作的实验演示结果     

Towards a new absolute frequency reference grid in the 28 THz range

We present a grid of absolute reference frequencies based on CO₂ (or N₂O) lasers locked to saturation peaks of heavy molecules. Frequency differences between OsO₄ peaks corresponding to adjacent CO₂ laser lines from P(12) to P(22) have been measured with 1 kHz accuracy. This set includes one ¹⁹²OsO₄ resonance whose absolute frequency is known with the same accuracy. This absolute grid is then used to provide an absolute calibration of the ν₃ band saturation spectrum of SF₆. We also find a 23 kHz average frequency difference between the CO₂ grid and the new OsO₄ grid which we interpret tentatively as a small extrapolation error from the R to the P branch frequencies of CO₂.     

Observation of the nuclear magnetic octupole moment of 133Cs

We describe our high-resolution measurements of the 133Cs 6p (2)P(3/2) state hyperfine structure. An optically narrowed diode laser excites perpendicularly a highly collimated atomic beam. The spectra are calibrated with a stable reference diode laser using a rf locking scheme allowing us to determine the splittings with an accuracy of < or =2 kHz, an order of magnitude better than previous results. The magnetic dipole a, electric quadrupole b, and magnetic octupole c hyperfine coupling constants are determined. The values we obtained are a=50.288 27(23) MHz, b=-0.4934(17) MHz, and c=0.56(7) kHz. This work represents the first observation of the magnetic octupole moment of the cesium nucleus. We carry out atomic-structure calculations and determine the nuclear electric quadrupole moment Q= -3.55(4) mb and nuclear magnetic octupole moment Omega=0.82(10) b x mu(N).