Laser Fluorescence Method for Detection of 129I and 127I Isotopes of Molecular Iodine with the Use of Kr Laser Radiation (647.1 nm)

The absorption spectra of the ¹²⁷I₂, ¹²⁷I¹²⁹I, and ¹²⁹I₂ isotopes of molecular iodine and the spectra of fluorescence excited by radiation of a Kr laser (λ=647.1 nm) were experimentally studied and calculated. A method for simultaneous determination of the concentration of ¹²⁷I and ¹²⁹I in gas mixtures (in particular, atmospheric air) is proposed.     

Possibility of separating the isotopes127I and129I with the aid of a photodissociation iodine laser

A method for separating iodine isotopes is proposed, based on the large difference between the rate constants of the excited I*(²P_1/2) and unaxclted iodine atoms with radicals CF₃ and with Cl₂ molecules, and on the possibility of selectively acting on the₁₂₇I atoms in the states²P_1/2 and²P_3/2 by radiation from a photodissociation R¹²⁷I iodine laser (λ = 1.315 μm). The possibility of separating the pure isotope¹²⁹I and the mixture¹²⁷I with¹²⁹I is investigated.     

Hyperfine structure of 127I2 and 129I2 optical absorption lines

The hyperfine structure of ¹²⁷I₂ and ¹²⁹I₂ rovibronic absorption lines was investigated using either laser induced fluorescence of a collimated molecular beam or saturated absorption in a cell. From the measurements a value for the quadrupole moment ratio ${}^{129}\text{Q}{}^{127}\text{Q}\text{=}\text{0.699}$ is deduced, in good agreement with the result obtained from pure quadrupole spectra in the rf range.     

Laser sounding of molecular iodine in the atmosphere

The lidar equation for the fluorescence of ¹²⁷I₂ molecules is numerically solved. All the radiation wavelengths of a copper vapor laser are considered with the aim of choosing the one that is the most appropriate for detection of the minimum possible concentration of iodine molecules when this laser is used as a radiation source of a fluorescence lidar.     

Wavelength stabilization of an Ar+ laser with an external129I2 absorption cell

Wavelength stabilization of the green Ar⁺ laser line at 514.5 nm by¹²⁹I₂ absorption was found to be more favourable than by¹²⁷I₂ absorption because the maximum of¹²⁹I₂ absorption is closer to the center of the 514.5 nm gain curve. A simple method for stabilizing a short air cooled laser with only one servo loop is given, yielding a stability of 10⁻⁸ λ.     

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.     

Multiphoton ionization of iodine atoms and CF<Subscript> 3</Subscript>I molecules by XeCl laser radiation

We report about effective ionization of iodine atoms and CF₃I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF₃I molecules is the I⁺ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(²P_3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I^*(²P_1/2). The ionization of the CF₃I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.     

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：     

Hyperfine spectra in iodine-129 at 612 nm

The complete hyperfine spectrum of a transition in ¹²⁹I₂ at a wavelength of 612 nm that overlaps the spectrum of ¹²⁷I₂ reported by Bennett and Cerez has been obtained, together with parts of the spectra of other transitions in ¹²⁹I₂ and ¹²⁷I₂. The lasers used for this work are described and the frequencies for the various hyperfine components are outlined.     

Development of accelerator mass spectrometry assisted by isotope-selective laser photodetachment for monitoring 129I

A prototype system was developed to investigate an isotope-selective laser photodetachment technique for a ¹²⁹I accelerator mass spectrometer. A pulsed ion source for negative iodine ions (I⁻) that employed laser ablation proved to be suitable for isotope-selective laser photodetachment. Laser photodetachment of pulsed negative iodine ions was estimated to have an efficiency of about 81% based on a model calculation for the prototype system with a tunable pulsed Ti:sapphire laser.     

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).     

Single-mode operation of an Ar+ laser with an intracavity I2 absorption cell

A multi-mode argon ion laser was furnished with an intracavity¹²⁷I₂ absorption cell for the purpose of mode suppression at the wavelength of 514.5 nm. Singlemode operation was achieved with an 8 cm long cell having a¹²⁷I₂ vapour pressure of 0.27 mbar (0.2 Torr).     

Laser excited fluorescence of molecular iodine <Superscript>127</Superscript>I and <Superscript>129</Superscript>I isotopes in the 632–637 nm spectral region

Experimental and theoretical studies of fluorescence of long-lived molecular iodine ¹²⁷I and ¹²⁹I isotopes excited by radiation emitted by frequency-tunable semiconductor laser were conducted for the first time. The results obtained demonstrate the potential of development of real-time laser detector of the isotopes in question.     

Resonanzstreuung am 202,8 keV-Niveau im J127

Using a gaseous Xe¹²⁷ source as exciting radiation resonance fluorescence from the 202.8 keV level in I¹²⁷ has been observed. The detection of the weak resonance effect in the presence of a strong 375 keV radiation was possible because of the high energy resolution of a Li-drifted Germanium detector. Assuming a transition energy ofQ _ECO =543 keV for the Xe¹²⁷-I¹²⁷decay the mean lifetime of the 202.8 keV level was determined to be τ=(0.56±0.09)nsec.     

Reactions of excited I*(2P1/2) and unexcited I(2P3/2) iodine atoms in perfluoroalkyl radicals

A method of investigating reactions of excited and unexcited atoms is discussed. It is based on pulsed photolysis of molecules with simultaneous passage of laser radiation through the working medium. The method proposed is used to investigate the reactions that accompany the photolysis of the molecules RI(CF₃I, n-C₃F₇I, i-C₃F₇I). The rate constants of the recombination of iodine atoms into I₂ in the presence of RI molecules are calculated for the atoms I(²P_3/2) and I*(²P_1/2), as are the recombination constants of the radicals R into R₂ and with the atoms I*(²P_1/2) and I(²P_3/2) into the RI molecule. It is shown that the I(²P_3/2) atoms are much more active in the recombination into Ia and RI than the I*(²P_1/2) atoms. The role of the investigated reactions in the kinetics of a photodissociation iodine laser (PDIL) is discussed. The results are compared with the published data.     

New determination of the 127I and 129I Mössbauer isomer shift calibration constants

New experimental data on the chemical changes δλ/λ of the probabilities λ of electron capture by ¹²³I and ¹²⁵I nuclei are treated taking into account the dependence of the exchange and overlap effect on the state of the electronic shell of the atom. The change δ?(0) in the electronic charge density at the iodine nucleus is evaluated and used for determination of the changes δ〈r²〉 in the mean square charge radius of the ¹²⁷I and ¹²⁹I nuclei on transition from the ground state to the first excited state. The δ〈r²〉 values determined, ?(10.0 ± 1.0) × 10^?3 fm² for ¹²⁷I and (13.0 ± 1.3) × 10^?3 fm² for ¹²⁹I, are in excellent agreement with the “best” values, recommended by Ruby and Shenoy.     

Mössbauer spectroscopy of laser annealed tellurium implanted silicon (II).129I

Laser annealed^129mTc-implanted silicon has been investigated using¹²⁹I Mössbauer spectroscopy. At least three dopedependent charge states of substitutional iodine are found. For heavily doped p-type Si a single line component S₁, with isomer shift S=0.96(4) mm/s w. r. t. Cu¹²⁹I and an effective Debye temperature ?′=196(3) K is observed. This component is attributed to I⁺⁺. For compensated Si a single line component, S₂, assigned to I⁺, with S=2.39 (4) mm/s and ?′=170 (3) K is found. For n-type Si, a component S₃, characterized at 4.2 K by S=2.15 (4) mm/s and a quadrupole splitting eQV_zz/h=452 (8) MHz (n?0)is observed. At higher temperatures S₃ shows quadrupole relaxation and its recoilless fraction becomes strongly anisotropic. This behaviour is explained on the basis of a transition from a static to a dynamic Jahn-Teller distortion. Component S₃ has been attributed to I⁰. In the spectra of compensated and n-type Si a less well-defined component Q, with parameters resembling those of S₃ but showing no quadrupole relaxation, is observed. This component has tentatively also been assigned to I^o. The results can be understood qualitatively on the basis of a simple MO-model.     

Variations of iodine-129 activities in various seaweed collected on the French channel coast

¹²⁹I, the only natural radioactive isotope of iodine (T_1/2=15.7×10⁶a), has been artificially produced since the end of the forties by the different nuclear, civil as well as military, activities leading to an increase of the background levels especially in the Northern hemisphere. In the marine environment, seaweed is known to accumulate iodine isotopes at high concentration levels. 16 seaweed species were collected at Goury (France), under the direct influence of discharges of authorised low-level radioactive liquid effluents of La Hague nuclear fuel reprocessing plant, in October 1998 and March 1999. ¹²⁹I/¹²⁷I ratios, computed with stable iodine concentration and ¹²⁹I activities measured on each sample, are significantly higher than the background levels. The heterogeneity of ¹²⁹I levels with seaweed species is studied as well as temporal variations that are related to the data of the ¹²⁹I liquid effluents released by the La Hague NRP. Concentration factors, estimated for all seaweed, agree with the recommended values and the ¹²⁹I activity in seawater was evaluated and shows a variation factor of 1.7 between the two sampling periods.     

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.     

Output power enhancement of the 632.8 nm monomode He-Ne/I2-laser

For the He-Ne/I₂-laser, a stable monomode operation has been realized when the tube pressure exceeds a certain level. An output power of more than 1 mW has been obtained at the 632.8 nm laser transition. Within the monomode tuning range of the laser, the d, e, f, g, and h, i, j iodine hyperfine components of the R(127) line of the 11–5 band of the B ³ II ⁺ _0u–X ¹⁺ _0g electronic transition have been observed. The mode selection method used makes it possible to increase the contrast of the iodine hyperfine components.