Identification of hyperfine structure components of the iodine molecule at 640 nm wavelength

The frequencies and the relative intensities of rotation-vibration transitions of ¹²⁷I₂, ¹²⁹I₂ and ¹²⁷I¹²⁹I near the HeNe laser emission wavelength of 640 nm have been calculated. Interpolation formulas for the differences of the electric quadrupole constants ΔeQq and of the spin-rotation constants ΔC of ¹²⁷I₂ are given. Most of the weak saturated-aborption lines, elsewhere published, have been identified as cross-over and forbidden lines of the transitions P(10)8-5 and R(16)8-5.     

飞秒光梳和碘稳频532nm Nd:YAG激光频率的测量

报道了中国计量科学研究院研制的基于掺钛蓝宝石(Ti:Sapphire)锁模飞秒脉冲激光器的飞秒光学频率梳装置，并利用此装置测量了碘稳频532nm(¹²⁷I₂R(56)32-10) Nd∶YAG固体激光器的频率，结果为 563260223512991±20Hz,相对不确定度为3.6×10^-14.这一数值是直接溯源到铯原子微波频率基准的光学频率测量结果.     

Quantitative high temperature absorption spectroscopy of NCO at 305 and 440 nm

A spectral survey of NCO absorption near the P₂ + ^pQ₁₂ head of the [A²Σ + (00⁰0)←X²Π_i(00¹0)] band was obtained at 1450°K, 0.6 atm using a remotely located cw ring dye laser source and a shock tube. Mixtures of hydrogen cyanide, oxygen and nitrous oxide diluted in argon were shock heated to provide a reproducible steady-state concentration of NCO, and narrow-line absorption was measured in repeated experiments with the laser set at different wavelengths. The peak absorption was found at 440.479 nm (vac). The experimental spectrum was compared with a theoretical model to yield an average Voigt parameter a ? 0.1. Additional experiments, in mixtures of cyanogen, oxygen and nitrous oxide diluted in argon, provided a known plateau level of NCO, which was used to infer an absolute absorption coefficient β(1450°K, 0.60 atm) = 110(-50, +130) cm^-1 atm^-1 at 440.479 nm. This value of β corresponds to an oscillator strength of 0.0026 for the (00⁰0←00¹0) band.Similar experiments were conducted to monitor the absorption around the R₁ head of the [B²Π_i(10¹0)←X²Π_i(00¹0)] band of NCO, using a frequency doubled cw ring dye laser. The observed spectrum displayed strong broadening, indicating predissociation of the upper state. At the peak absorption wavelength (304.681 nm, vac), we inferred β(1470°K, 0.63 atm) = 40(-19, +48) cm^-1 atm^-1 and a ? 9. This value of β corresponds to an oscillator strength of 0.0031 for the (10¹0←00¹0) band.     

Beat frequency intercomparisons of127I2 stabilized ion lasers at 514.5 nm

International comparisons of I₂ stabilized ion lasers operated at 514.5 nm have shown a laser frequency reproducibility of 2·10⁻¹⁰ v to 5·10⁻¹² v. These results encouraged the international acceptance of the wavelength value λ_vac=514.673467 for thea ₃ hyperfine component of the¹²⁷I₂ line 43-0P(13).     

A frequency-doubled frequency-stabilized cw ring dye laser for spectroscopy: A study of the λ = 293.3 nm transition in In1

In this letter a frequency-doubled frequency-stabilized CW ring dye laser for the wavelength region 292–305 nm is described. 500 μW U.V. power combined with a 2 MHz linewidth and a 7 GHz scanwidth has been obtained by intracavity frequency doubling in an ADA crystal. The set-up has been tested on the hyperfinestructure of the λ = 293.3 nm transition 5p²P_{$\text{3}\text{2}$} → 7s²S_{$\text{1}\text{2}$} in In1.     

The violet emissions produced by laser excitation of Na vapor in the 570–595 nm region

We have observed atomic Na and molecular Na₂ emissions in the violet region when Na vapor in a heatpipe (～10³—10¹⁶ atoms/cm³) is irradiated with a pulsed dye laser with output wavelength in the 570–597 nm region. The Na atomic emissions probably result from recombination of Na⁺ + e^- and energy-pooling involving highly excited atoms and molecules, while the diffuse violet emission bands are probably produced through collisions among excited Na atoms and Na₂ molecules.     

Generation of cw 243 nm radiation and application to laser spectroscopy of the strontium isotopes

Intra-cavity second harmonic generation in a ring dye laser using lithium formate monohydrate has been observed to produce tunable cw UV radiation around 243 nm with single frequency powers of up to 1.4 mW. This wavelength region is of particular interest in the context of Doppler-free spectroscopy of atomic hydrogen. The radiation was used to excite an atomic beam of strontium to study the transition 5s^{2 1}S₀-4d5p ¹P₁ of Sr I. The isotope shifts were determined as follows: ⁸⁸Sr-⁸⁷Sr 123.7(8) MHz; ⁸⁸Sr 285.0(8) MHz; ⁸⁸Sr-⁸⁴Sr 600.1(9) MHz. The values are compared with results for other lines and muonic isotope shifts to obtain the specific mass shift and field shift in this transition and to study the configuration mixing effects. The hyperfine structure of ⁸⁷Sr was not resolved, the intervals being very much less than the measured linewidth of 25 MHz.     

Interferometric frequency measurements of 130Te2 transitions at 486 nm

Doppler-free spectra of ¹³⁰Te₂ have been investigated in the region of 486 nm, close to the Balmer-β transitions atomic hydrogen and deuterium. The frequency ratios between a 633 nm He-Ne laser stabilized to the 11-5 R(127) “i” transition in ¹²⁷I₂ and two of these ¹³⁰Te₂ Doppler-free components have been measured interferometrically to a precision of 2 parts in 10¹⁰ (one standard deviation). These measured components constitute useful transfer standards for the measurement of absolute frequencies of both the Balmer-β transitions and the 243-nm two-photon 1S-2S transitions in hydrogen and deuterium.     

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.     

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.     

All solid-state continuous-wave Nd:YAG laser at 1319 and 659.5 nm under direct 885 nm pumping

The continuous-wave high efficiency laser emission of Nd:YAG at the fundamental wavelength of 1319 nm and its 659.5-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 885 nm (on the ⁴ F _3/2 → ⁴ I _13/2 transition). An end-pumped Nd:YAG crystal yielded 9.1 W at 1319 nm of continuous-wave output power for 18.2 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power is 0.55. Furthermore, 5.2 W 659.5 nm red light is acquired by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 0.286. Comparative results obtained for the pump with diode laser at 808 nm (on the ⁴ F _5/2 → ⁴ I _13/2 transition) are given in order to prove the advantages of the 885 nm wavelength pumping.     

CW ultraviolet saturation spectroscopy of the 6p 3P0-9s 3S1 transition in mercury at 246.5 nm

We have measured the even isotope structure of the 6p ³P₀-9s ³S₁ transition in mercury at 246.5 nm using saturated absorption spectroscopy with radiation produced as the sum frequency of a 363.8 nm argon ion laser and an LD700 ring dye laser in ADP. This is the first use of cw sum-frequency mixing in nonlinear laser spectroscopy in the ultraviolet. No previous cw Doppler-free measurements have been reported at wavelenghts below 294.5 nm     

High-efficiency direct-pumped Nd:YVO4-LBO laser operating at 671 nm

The continuous-wave high-efficiency laser emission from Nd:YVO₄ at the fundamental wavelength of 1342 nm and its 671 nm second harmonic obtained by intra-cavity frequency doubling in an LBO nonlinear crystal are investigated under pumping by diode laser at 880 nm (on the ⁴F_3/2→⁴I_13/2 transition). The end-pumped Nd:YVO₄ crystal yielded a continuous-wave output power of 9.6 W at 1342 nm for 18.9 W of absorbed pump power. The slope efficiency measured with respect to the absorbed pump power is 60%. An output of 5.5 W at 671 nm was obtained by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 29%. Comparative results obtained for the pump with a diode laser at 808 nm (on the ⁴F_5/2→⁴I_13/2 transition) are given in order to prove the advantages of the 880 nm wavelength pumping.     

Narrow-band UV radiation (250–260 nm) from intracavity doubling a single-mode ring dye laser

Generation of continuous-wave, tunable UV radiation (250–260 nm) by intracavity doubling a coumarin-515 ring dye laser is described. A cooled (200–280 K) ADP crystal with end faces cut at Brester's angle is placed inside the laser ring cavity which has been compensated for astigmatism and coma. UV output powers at 254 nm of 120 μW and 60 μW are achieved with the laser operating multimode (bandwidth ? 20 GHz) and single-mode (bandwidth ? 50 MHz), respectively. Continuous single-mode scans over the 253.7 nm mercury profile demonstrate sub-Doppler resolution of the Hg 6s6p ³P^O₁ - 6s²¹S₀ transition.     

127)I2在633nm波段的超精细强谱线及稳频半导体激光器

报道了观察到的碘分子（¹²⁷I₂）在633nm波段的5组超精细强谱线,并对每组谱线的频率间距及相应振转能级的跃迁强度作出了计算,结果和实验吻合得很好．利用计算结果,对这5组谱线对应的振转能带作出了甄别．由于这些新谱线比用于氦氖激光器稳频的R（127）11.5跃迁强几百倍,因此利用这些新谱线作为半导体激光稳频的参考谱线,得到了功率为3mW的激光输出,这种半导体激光可成为新型光频标． 关键词：     

Simultaneous dual-wavelength laser operation at 1342 and 946 nm in two laser crystals and their sum-frequency mixing

A sum-frequency yellow-green laser at 554.9 nm is reported by this paper, 946 nm wavelength is obtained from ⁴F_3/2-⁴I_9/2 transition in Nd:YAG and 1342 nm wavelength is obtained from ⁴F_3/2-⁴I_13/2 transition in Nd:YVO₄. Using a doubly folded-cavity type-II critical phase matching KTP crystal intra cavity to make 946 nm laser from Nd:YAG and 1342 nm laser from Nd:YVO₄ frequency summed, with incident pumped power of 30 W in Nd:YAG and 20 W in Nd:YVO₄, TEM₀₀ mode yellow-green laser at 554.9 nm at 1.15 W is obtained and its M² factor is less than 1.22. The experimental results show that the Nd:YAG and Nd:YVO₄ crystals intra-cavity sum-frequency mixing is an effective method for yellow-green laser and it can be applied to other two laser crystals to obtain more all-solid-state lasers with different wavelengths.     

Photophysical parameters and fluorescence quenching of 7-diethylaminocoumarin (DEAC) laser dye

The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10⁻³ mol dm⁻³ of DEAC gives laser emission in the blue region on pumping with nitrogen laser (λ_ex=337.1 nm). The laser parameters such as tuning range, gain coefficient (α), emission cross section (σ_e), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl₄ at a wavelength of 366 nm. The values of photochemical yield (?_c) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH₃CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex.     

表面层对1 064 nm高反射镜损伤阈值影响

 采用电子束蒸发的方法制备了３种具有不同表面层材料及结构的中心波长为1 064 nm的零度高反镜,３种膜系表面层分别为1/4波长光学厚度的HfO₂,1/2波长光学厚度的SiO₂,以及1/4波长光学厚度的SiO₂。光谱测试表明：三者在1 064 nm处均有较高的反射率（高于99.8%）,利用热透镜的方法测量得到３个膜系辐照激光正入射情况下,薄膜对光的吸收比例分别为3.0×10^-6,5.0×10^-6和6.5×10^-6,其损伤阈值分别为32.5,45.2和28.4 J/cm²。并在膜层内部电场分布和膜层材料物理特性的基础上分析了３种不同表面层膜系吸收和损伤阈值差别的原因。     

A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb

This paper reports that two identical external-cavity-diode-laser (ECDL) based spectrometers are constructed at 634 nm referencing on the hyperfine B-X transition R(80)8-4 of ¹²⁷I₂. The lasers are stabilized on the Doppler-free absorption signals using the third-harmonic detection technique. The instability of the stabilized laser is measured to be 2.8×10^-12 (after 1000 s) by counting the beat note between the two lasers. The absolute optical frequency of the transition is, for the first time, determined to be 472851936189.5 kHz by using an optical frequency comb referenced on the microwave caesium atomic clock. The uncertainty of the measurement is less than 4.9 kHz.     

Natural radiative lifetimes in the2S1/2 and2D5/2,3/2 sequences of aluminum

Natural radiative lifetimes have been measured for the 3s ² ns ² S _1/2 (n≦10) and 3s ² nd ² D _5/2,3/2 (n≦11) sequences of aluminum using pulsed laser excitation of an atomic beam. The investigated states were populated from the ground configuration using UV pulses of wavelength down to 210 nm produced by a Nd: YAG- or an excimer-pumped dye-laser system. TheS-state lifetimes increase regularily with increasing principal quantum number but this is not the case for theD sequence.