Isotope shift and hyperfine structure measurements in titanium I

High accuracy measurements of hyperfine structure due to⁴⁷Ti and⁴⁹Ti in the 3d ² 4s ² a ³ F ₂?3d ² 4s4p z ⁵ D ₁ absorption line at σ=18482.772 cm^?1 have been performed by use of a Doppler-free experiment, where a beam of titanium atoms is crossed by a CW single mode tunable dye laser. They have allowed for the determination of isotope shifts between⁴⁶Ti,⁴⁷Ti,⁴⁸Ti,⁴⁹Ti and⁵⁰Ti. By use of accurate values of mean square nuclear charge radii for the even isotopes, it has been possible to separate mass shifts from field shifts and to determine accurate values for the mean square nuclear charge radii of⁴⁷Ti and⁴⁹Ti. The field shift presents a marked odd-even staggering.     

CO2对790nm附近水线的压力加宽和位移

采用高灵敏的激光光腔衰荡光谱技术研究了CO2对160水分子v^2＋3v^3振动带跃迁线的压力诱导效应．为了抑制水的自碰撞效应,水的压力在实验中低于0．5Torr．基于铷原子吸收线和超稳法布里-珀罗标准确定了跃迁谱线高达10^-5cm^-1精度的绝对频率．采用软碰撞模型对吸收线进行模拟,获得了对应的线形参数．     

High precision density studies near the smectic A-nematic tricritical point

We have carried out very accurate density measurements (with a precision of ±5 × 10^-5g cm^-3) near the smectic A-nematic transition in binary mixtures of 4-n-nonyl-4'-cyanobiphenyl (9CB) and 4-n-decyl-4'-cyanobiphenyl (10CB). The transition crosses over from second to first order as the temperature range of the nematic phase decreases. For mixtures with the shortest nematic range the data deviate noticeably from a single power law behaviour. Such a deviation is an indication of the first order nature of the transition. Very good fits to a single power law have been obtained for pure 9CB and the x = 0·04 mixture where x is the mole fraction of 10CB in 9CB. The critical exponent obtained from the power law fitting has enabled us to locate the tricritical point to be very close to x=0·04, which is in agreement with the results obtained previously by high resolution calorimetric [1] and X-ray scattering studies [2].     

Laser-molecular beam measurement of hyperfine structure in the I2 spectrum

Very high resolution measurements of hyperfine structure on the P(13) and R(15), 43?0, $\text{3}{}_{\mathrm{gp}}{}_0{}^{\mathrm{+}}{}_{\mathrm{u}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transitions in iodine 127 were made using laser molecular beam spectroscopy. The observed linewidth was 300 kHz (fwhm) giving a resolution of 5 × 10^?10 The observed spectrum was fitted to obtain a quadrupole coupling strength difference of ΔeQq = 1906 ± 2 MHz and a spin rotation interaction strength difference of ΔC_I = 181 ± 7 kHz between the upper and lower levels of the P(13) transition. For the R (15) transition ΔeQq = 1905 ± 2 MHz and ΔC_I = 167 ± 5 kHz.     

High precision retention time measurements in gas chromatography. I. A simple differentiating time printer for large sample sizes

Summary A differentiating time printer (DTP) apparatus has been constructed from standard laboratory equipment by connecting a differentiating CR circuit via an operational amplifier to an electronic temperature regulator that triggers the print out of a line frequency driven register. The electronic resolution is 0.1 s, giving a relative standard deviation _rel, which is determined by the stability of the line frequency at sufficiently long retention times. In Lund this corresponds to a best _rel = 0.02% and to a mean _rel = 0.03%. For late and broad peaks in real GC the noise caused the print-out of extra time values, especially with fronting peaks from ordinary 1/8 columns. However, a comparison with the simultaneously recorded chromatograms was generally sufficient to pick out the proper retention times. For large sample sizes the corrected retention time t increased with peak height, the later the peak in the chromatogram. The In t _n+1 /t _n values from a series of n-paraffins showed good linear correlations with peak height h_n+1 and peak area A_n+1, giving standard deviations around the line approaching that expected from _rel. The accuracy of the system was mainly determined by the effect of a non-zero triggering level on the derived signal and by the time displacement expected from a large time constant. A rough estimate of the time error was made by simulating GC peaks with a cosine wave generator.     

Collision-induced absorption in the O2 B-band region near 670 nm

We have determined the collision-induced absorption (CIA) spectrum in the O(2) B-band in pure oxygen. We present absolute extinction coefficients of the minimums in between rotational lines using cavity ring-down spectroscopy. The measured extinction is corrected for the B-band magnetic dipole absorption using a model which includes line-mixing. The remaining extinction consists of collision-induced absorption and Rayleigh scattering. We retrieve the magnitude of the Rayleigh scattering and the CIA spectrum based on their individual different behavior with density. The CIA spectrum of the B-band resembles that of the oxygen A-band in shape but not in magnitude. The contribution of CIA to the total B-band absorption is 40% higher in comparison to that of the A-band.     

High precision measurements of 17O/16O and 18O/16O ratios in H2O

We have optimized the method of water fluorination using the solid reagent CoF3 to produce O2. This allows isotope ratio measurements by dual-inlet mass spectrometry with very high precision of 0.01 to 0.03/1000 for both delta17O and delta18O. Using this method, delta17O and delta18O of atmospheric O2 were determined as 12.08 and 23.88/1000 vs. VSMOW, respectively. Likewise, delta17O and delta18O of GISP were -13.12 and -24.73/1000, and for SLAP they were -29.48 and -55.11/1000 vs. VSMOW, respectively. Analysis of these data in a ln(delta17O + 1) vs. ln(delta18O + 1) plot yields a line with a regression coefficient (lambda) of 0.5279 +/- 0.0001 (R2 = 0.999999). We also determined the fractionation factors 17alpha and 18alpha in liquid-vapor equilibrium, and found that the ratio ln 17alpha/ln 18alpha is constant (0.529 +/- 0.001) over the temperature range 11.4 to 41.5 degrees C.     

Photofragment translational spectroscopy of n-C3H7I and i-C3H7I near 280 and 304 nm

The photodissociation dynamics of propyl iodides n-C3H7I and i-C3H7I near 280 and 304 nm has been investigated with our mini-TOF photofragment translational spectrometer. When a single laser is applied for both the photodissociation of parent molecules and the REMPI of I atom photofragments, the TOF spectra of photofragments I*(2P1/2) and I (2P3/2) are obtained at four different wavelengths for these two iodides. For n-C3H7I, some small vibrational peaks are partially resolved (with separation of approximately 522 cm-1, corresponding to the RCH2 deformation frequency of the fragment n-C3H7) at 281.73, 279.71, and 304.67 nm. These results show that the RCH2 deformation is mostly excited. For i-C3H7I, we obtain some partially resolved vibrational peaks (with separation of approximately 352 cm-1, corresponding to the HC(CH3)2 out-of-plane bending frequency of the fragment i-C3H7) at 281.73 nm only. For n-C3H7I, the partitioning values of the available energy Eint/Eavl are 0.48 at 281.73 nm and 0.49 at 304.02 nm for the I* channel, and 0.52 at both 279.71 and 304.67 nm for the I channel. These energy partitioning values are comparable with the previous results at different wavelengths in the literature. For i-C3H7I, the Eint/Eavl values are 0.61 at 281.73 nm, 0.65 at 304.02 nm for the I* channel, and 0.62 at 279.71 nm, 0.49 at 304.67 nm for the I channel. The potential-energy-surface crossing and the beta values have also been discussed.     

ΔF = ±2 transitions in the hyperfine spectrum of Er I

The occurrence of 15ΔF=±2 transitions in the hyperfine spectrum of five lines of Er I was observed by means of high-resolution laser-atomic-beam spectroscopy. These normally forbidden transitions are caused by an external magnetic field which mixes closely lying hyperfine levels that have neighbouringF quantum numbers. If the Zeeman splittings under the applied magnetic field are small compared to the hyperfine splittings, the intensities of theΔF=±2 components are proportional to the square of the magnetic field strength. Under the variation of the laser intensity theΔF=±2 transitions show the same behaviour as homogeneously broadenedΔF=0, ±1 transitions. The relative intensities between theΔF=±2 components as well as the intensity ratios of theΔF=±2 to neighbouringΔF=±1 components are studied and interpreted in terms of first order perturbation theory.     

Photodissociation dynamics of CH(2)Br(2) near 234 and 267 nm

The photodissociation dynamics of CH(2)Br(2) was investigated near 234 and 267 nm. A two-dimensional photofragment ion velocity imaging technique coupled with a [2+1] resonance-enhanced multiphoton (REMPI) ionization scheme was utilized to obtain the angular and translational energy distributions of the nascent Br ((2)P(3/2)) and Br* ((2)P(1/2)) atoms. The obtained translational energy distributions of Br and Br* are found consist of two components which should be come from the radical channel and secondary dissociation process, respectively. It is suggested that the symmetry reduction from C(2v) to C(s) during photodissociation invokes a non-adiabatic coupling between the 2B(1) and A(1) states. Consequently, the higher internal energy distribution of Br channel than Br* formation channel and the broader translational energy distribution of the former are presumed correlate with a variety of vibrational excitation disposal at the crossing point resulting from the larger non-adiabatic crossing from 2B(1) to A(1) state than the reverse crossing. Moreover, the measured anisotropy parameter beta indicate that fragments recoil along the Br-Br direction mostly in the photodissociation.     

Photodissociation channels for N2O near 130 nm studied by product imaging

The photodissociation of N(2)O at wavelengths near 130 nm has been investigated by velocity-mapped product imaging. In all, five dissociation channels have been detected, leading to the following products: O((1)S)+N(2)(X (1)Sigma), N((2)D)+NO(X (2)Pi), N((2)P)+NO(X (2)Pi), O((3)P) + N(2)(A (3)Sigma(+) (u)), and O((3)P) + N(2)(B (3)Pi(g)). The most significant channel is to the products O((1)S) + N(2)(X(1)Sigma), with strong vibrational excitation in the N(2). The O((3)P) + N(2)(A,B):N((2)D,(2)P) + NO branching ratio is measured to be 1.4 +/- 0.5, while the N(2)(A) + O((3)P(J)):N(2)(B) + O((3)P(J)) branching ratio is determined to be 0.84+/-0.09. The spin-orbit distributions for the O((3)P(J)), N((2)P(J)), and N((2)D(J)) products were also determined. The angular distributions of the products are in qualitative agreement with excitation to the N(2)O(D (1)Sigma(+)) state, with participation as well by the (3)Pi(v) state.     

Large-scale MCHF calculations of hyperfine structures in nitrogen and oxygen

The hyperfine structure constants for the 1s ²2s ²2p ³ -⁴ S ^o ground state in nitrogen and the 1s ²2s ²2p ³3s ⁵ S ^o excited state in oxygen are calculated using the MCHF Atomic Structure Package. The single excitation picture is explored through the use of compact wave functions allowing radial non-orthogonalities. Electron correlation is described through numerical multiconfiguration Hartree-Fock calculations for configuration expansions obtained by allowing all single and double excitations from the reference configuration to an active set of orbitals. The latter is increased in a systematic way allowing the convergence of the hyperfine parameters to be studied. Three- and four-particle effects are shown to be important and are taken into account in a sequence of large configuration interaction calculations. The final results are in good agreement with experiment.     

Multiphoton dissociative ionization of tert-pentyl bromide near 265 nm

We report on the photodissociation dynamics of tert-pentyl bromide near 265 nm investigated by time-sliced velocity map imaging. The speed and angular distributions have been analyzed for both the ground-state Br((2)P(3∕2)) atom (denoted Br) and the spin-orbit excited-state Br((2)P(1∕2)) atom (denoted Br*). The speed distributions of Br and Br* atoms are all found to consist of three Gaussian components, which correlate to three independent dissociation pathways on the excited potential energy surfaces: (1) the high translational energy (E(T)) component from the prompt dissociation along the C-Br stretching mode, (2) the middle E(T) component from the repulsive mode along the C-Br stretching coupled with some bending motions, and (3) the low E(T) component from the repulsive mode along the C-Br stretching coupled with more bending motions. More interestingly, we have also observed the tert-C(5)H(11)(+) ions in 263-267 nm. The near-zero kinetic energy distributions extracted from the three tert-C(5)H(11)(+) images near 265 nm show the typical characteristics that are attributable to multiphoton dissociative ionization, suggesting the existence of a neutral superexcited state of the parent tert-pentyl bromide molecule. The contribution of bromine atoms formed in this dissociative ionization channel adds in the total relative distribution of low E(T) component in the Br*(Br) formation channel, which reasonably explains the abnormal distributions observed in between the middle and low E(T) components in the Br*(Br) formation channel.     

VCSEL based detection of water vapor near 940nm

A vertical-cavity surface-emitting laser (VCSEL) was used to study the absorption spectrum of water vapor in the 940nm region. Measurements were performed in ambient air at room temperature and in a hydrogen-oxygen flame over the temperature range of 1500-1800K. Several rotational absorption lines within the 2v1 + v3 vibrational band were measured. The absorption spectra were well resolved, which demonstrates the feasibility of VCSEL-based spectroscopic measurements of water vapor at room and high-temperature in this spectral region. The results were in good agreement with the values obtained from the HITRAN-96 database.     

ΔF = 2–6 transitions in the hyperfine spectrum of λ = 601.8 nm line of 151Eu

The magnetic field effect of the a ⁸ S _1/2-z ⁸ P _9/2, F = 7 transition lines of ¹⁵¹Eu in magnetic fields up to 400 Gauss has been studied by using laser-atomic-beam-spectroscopy. δF = 2–6 transitions were observed. Results show that the transitions originate from the mixing of the Zeeman states induced by the magnetic field. The condition favourable to observation of the |δF| ≥ 2 transitions especially the transitions with high |δF| values discussed     

Detailed study of fine and hyperfine structures in rotational spectra of the free fluoroformyloxyl radical FCO2

More than 160 new hyperfine components of rotational transitions of the free fluoroformyloxyl radical FCO(2) have been measured using the Prague millimeter wave high resolution spectrometer. The frequencies of these transitions together with the previously measured data were analyzed in detail and precise values of magnetic hyperfine and fine parameters were obtained. These new parameters significantly improve the values of previously determined hyperfine parameters which were rather unreliable. The new fine and hyperfine parameters obtained in this study are compatible with those of the simultaneously electron paramagnetic resonance study. Besides that, significantly improved ground state rotational and centrifugal distortion constants of the fluoroformyloxyl radical were derived.     

High precision titrimetry: An examination of the attainable precision

A re-examination and critical assessment of the mechanical precision of titrimetric processes, with particular reference to the drainage errors of burettes, has been made and some manipulative improvements suggested.The piputte-dilution method offers a useful improvement in the precision of volumetric methods, further increase in mechnical precision affords little or no improvement in accuracy of determination.     

Test of advanced hyperfine structure theory by precision radio-frequency and laser spectroscopy in molybdenum

The hyperfine structure splittings of 32 even parity states and of 26 odd partity states of molybdenum have been measured by atomic beam magnetic resonance and by laser induced fluorescence. The analysis of the hyperfine structure data of the even parity configurations (4d+5s)⁶ yields experimental evidence for second order hyperfine interactions. In addition, theg _J factors of 19 fine structure levels have been determined in order to test the quality of intermediate coupling wave functions for the (4d+5s)⁶ configurations.     

Current interlaboratory precision of exchangeable soil fraction measurements

 In addition to conventional aqua regia and EDTA extracts for monitoring trace metals in soils, the technique of examining exchangeable soil fractions has been suggested to estimate soil contamination and trace metal availability to plants. In order to establish a useful method for soil monitoring, interlaboratory precision as a primary selection criterion has been investigated. In order to assess the quality of data provided by laboratories participating in the organization of the Austrian Governmental Agricultural Research Institutes (ALVA), three soil samples have been analysed in a common ring test, annually, for the last 20 years. In addition to the annual list of parameters used for soil monitoring, within ALVA two NH₄-acetate extracts were run in 1994, three NH₄-acetate and NH₄NO₃ extracts in 1995 and three LiCl extractions in 1998. The procedures were tested for analytical precision and environmental indications in up to 12 laboratories, with respect to Cd, Cr, Cu, Ni, Pb and Zn. Due to the low extraction efficiency, for determinations in the resultant solutions, graphite furnace AAS was preferably selected, except for Zn and Cu. Flame-AAS and ICP-OES were not sensitive enough for non-contaminated sites. Interlaboratory precision of the data was in the range 10–65% coeff.var., and thus within the range of data given in the appendix of DIN 19730 (NH₄NO₃), as well as in a previous BCR report. Indications from exchangeable fractions seemed to be good for Zn and Cu, whereas they were impossible for Cr. Received: 25 October 1998 / Accepted: 26 January 1999