Experimental and theoretical study of the hyperfine structure in the (5d+6s)96p configurations of Pt I

The hyperfine structure of the odd configurations 5d ⁹6p and 5d ⁸6s6p was studied with laser optogalvanic spectroscopy and high resolution interferometry in a platinum hollow cathode. A parametric hyperfine structure analysis for the configurations (5d+6s)⁹6p with 10 excited odd-parity levels was performed for¹⁹⁵Pt. We obtained one-electron hfs parameters,a _5d ⁰¹ =1160(320) MHz,a _6s ¹⁰ =35600(5300) MHz anda _6p ⁰¹ =1300(780) MHz for the configuration 5d ⁸6s6p. The corresponding $\left\langle {r^{ - 3} } \right\rangle _{nl}^{k_s k_l } $ values are compared with those known for other 5d-elements.     

Electric and magnetic hyperfinestructure investigations in the 5s 25p 3 and 5s 25p 26s Configurations of121, 123Sb

Optical hyperfinestructure investigations in several spectral lines were carried out in the Sb-I spectrum from which for the first time accurate values of the hfs-splitting constantsA andB of the ground configuration 5p ³ and also for five of the eight levels of the first excited configuration 5p ²6s were obtained. With these parameters the influence of core polarization effects is calculated to bea _c= ?6.6(4) mK, (equivalent to a magnetic field of ?283(20) kG perp-electron spin). The quadrupole momentQ ₁₂₁= ?0.36(4) b (including Sternheimer correction) was obtained with the experimental valuesb _3/2= ?14.3(1.0) mK and 〈r ^?3〉 =11.2(3) a.u. andQ ₁₂₃= ?0.49(5) b withb _3/2= ?19.9(1.0) mK resp. This evaluation also yields the relativistic correction factor η= ?(C″/C′) · S _r/R′ _r=1.13(2). —For the first time, too, isotope shift investigations in Sb-I lines were possible which permit to determine the isotope shift constant βC _exp= 40(10) mK, and a value δ〈r ²〉^{121, 123}=0.12(4) fm² for the change in the mean square nuclear charge radius between¹²¹Sb and¹²³Sb which is about 50 percent of the prediction of the unified nuclear model.     

Line Shift Investigations for Different Isotopomers of Carbon Monoxide

Line shift coefficients for five lines of five different isotopomers in the fundamental band of CO in the spectral region near 2058 cm⁻¹were measured using a three channel lead salt diode laser spectrometer. The study includes the linesP(3) of¹³C¹⁷O,R(3) of¹³C¹⁸O,P(9) of¹²C¹⁸O,P(10) of¹³C¹⁶O, andP(21) of¹²C¹⁶O, and covers collisions with N₂, O₂, H₂, D₂, He, Ne, Ar, Kr, and Xe. Line shifts of the isotopomers¹³C¹⁶O,¹²C¹⁸O,¹³C¹⁸O, and¹³C¹⁷O were determined for the first time. Within the experimental uncertainty no significant dependence of the shift effect on the isotopomer was found. TheR-branch line under study shows a smaller line shift coefficient than aP-branch line with a similar rotational quantum number. With increasing mass of the noble gas perturber the absolute size of the shift coefficient increases. Moreover self- and nitrogen-broadening coefficients for the isotopomer lines were determined. Compared to previous measurements no significant deviations between different isotopomers were observed.     

Trace analysis of polycyclic aromatic hydrocarbons using calixarene layered gold colloid film as substrates for surface‐enhanced Raman scattering

A surface‐enhanced Raman scattering (SERS) active substrate for the detection of polycyclic aromatic hydrocarbons (PAHs) was developed, which used 25, 27‐dimercaptoacetic acid‐26, 28‐dihydroxy‐4‐terbutyl calix[4]arene (DMCX) to functionalize a gold colloid film. This SERS‐active substrate prepared by self‐assembly method exhibits a high sensitivity, especially for the detection of PAHs. With the use of this SERS‐active substrate and with the application of the shifted excitation Raman difference spectroscopy (SERDS) technique, Raman signals of pyrene and anthracene in aqueous solutions at low concentration level (500 pM) can be obtained. Moreover, because PAHs are blocked from being directly adsorbed on gold colloid by DMCX and the photochemical reactions of adsorbates are avoided, the Raman bands of PAHs adsorbed on DMCX‐fuctionalized gold colloid film can be one‐to‐one correspondence with those of solid PAHs, and additionally, this SERS‐active substrate can be easily cleaned and reused. The obtained results demonstrate that the DMCX‐functionalized gold colloid films prepared by self‐assembly method have great potential to be developed to an in situ PAHs detection substrate. Copyright © 2012 John Wiley & Sons, Ltd.     

SERS signal response and SERS/SERDS spectra of fluoranthene in water on naturally grown Ag nanoparticle ensembles

We present experimental results of the time‐dependent Raman signal response of fluoranthene adsorbed on a naturally grown Ag nanoparticle ensemble, which serves as surface enhanced Raman scattering (SERS) substrate. In addition, SERS characteristics such as the concentration‐dependent calibration curves and the limit of detection (LOD) for fluoranthene in distilled water will be shown. The SERS substrate was prepared by Volmer–Weber growth under ultrahigh vacuum condition and exhibits a plasmon resonance wavelength at 491 nm. For the measurement of SERS signal response and SERS/shifted excitation Raman difference spectroscopy spectra of fluoranthene in water, experimental Raman setup containing a microsystem light source with two emission wavelengths (487.61 nm and 487.91 nm) was used. We experimentally demonstrate that the maximum SERS intensity is achieved 9 min after changing the analyte concentration from 0 nmol/l to 600 nmol/l. This response time is explained by a time‐dependent adsorption of the probe molecules onto the nanoparticles. The LOD for fluoranthene in water was evaluated applying shifted excitation Raman difference spectroscopy (SERDS) at different molecule concentrations. For SERDS, two emission wavelengths of a prototype microsystem light source have been used for Raman excitation. The experimental results reveal that the LOD for the probe molecules is very low. Experimentally, we have detected a fluoranthene concentration of only 4 nmol/l, which is very close to our estimated LOD of 2 nmol/l. Thus, the presented Raman setup, with a SERS substrate, whose plasmon resonance coincides with the excitation wavelength for SERS measurements, is well suited for in‐situ trace detection of pollutant chemicals in water. Copyright © 2013 John Wiley & Sons, Ltd.     

A cw AgGaS2 difference frequency spectrometer with diode lasers as pump sources

2 and two diode lasers as pump sources and experiments with this setup are presented. In contrast to the majority of known applications of the difference frequency mixing with solid state or gas lasers, we apply two single mode diode lasers with emission wavelengths of 690 nm and 805 nm, respectively. By fixing the emission wavelength of one diode laser and tuning the wavelength of the second laser, by changing temperature or excitation current, we can cover typically 0.87 cm^-1 (FWHM) in good agreement with recently published data and theory. With an input power of 20 mW and 6 mW we achieved an output power in the nW-range. To demonstrate the capabilities of the spectrometer we scanned CO and OCS absorption lines near 2107 cm^-1. From these experiments we deduce an overall signal-to-noise ratio of 1000:1 and a spectral resolution better than 30 MHz. With such parameters a trace gas detection of CO at sub-ppm level will be possible. Received: 19 August 1996/Revised version: 5 November 1996     

Crossed-second-order-effects of the isotope shift and hyperfine-structure parameters in the Eu I configuration 4f 7 6s6d

In the Eu I configuration 4f ⁷ 6s6d the isotope shift (IS) and hyperfine-structure (hfs) of the termse ⁶ D ande ¹⁰ D were determined from fourteen transitions (4f ⁷ 6s6d-4f ⁷ 6s6p) with computer supported interference spectroscopy. From the IS of altogether nine levels of 4f ⁷ 6s6d the crossed-second-order-parameterg ₃(4f,6s)=?0.90(6)mK was evaluated. The ratiog ₃/G ₃=?4.4(3)·10^?6 (G ₃: Slater Integral of the fine structure) is of the same size as that from five other independent investigations and one theoretical value. The single electron hfs splitting constantsa _4f ¹⁰ =?1.9(3)mK,a _6s ¹⁰ =391(3)mK, anda _6d ¹² =0.9(3)mK were also evaluated and are compared with those of other Eu 4f ⁷ 6snl configurations.     

Hyperfine structure in the configuration 4f 136s7s of Tm I

Doppler-free saturation absorption spectroscopy was applied on an atomic thulium vapour in a see-through hollow cathode for the determination of precise values for the magnetic dipole hyperfine structure constantsA of 6 levels of the configuration 4f ¹³ 6s7s. A parametric analysis of the hyperfine structure has been performed, using wave-functions from a fine structure calculation, which leads to one-electron hyperfine structure parametersa _4f ⁰¹ =?500(6) MHz,a _6s ¹⁰ =?5058(47) MHz, anda _7s ¹⁰ =?1012 MHz.     

Crossed-second-order effects in the isotope shift for170–166Er and168–166Er in the configuration 4f 12 6s 2

High resolution interference and intermodulated optogalvanic saturation spectroscopy has been applied for isotope shift (IS) studies in the ground-configuration 4f ¹² 6s ² of ErI. For the isotope pairs^170–166Er and^168–166Er the results confirm a strongJ- and term dependence of the IS caused through crossed-second-order (CSO) effects. We performed a parametric analysis to evaluate the CSO-parametersz _4f for the interpretation of theJ-dependence andT(³ H),T(³ F),T(¹ G) to describe the term dependence. The following parameter values (in MHz) were determined, for^170–166Er:z _4f =40.1(0.6),T(³ F)=?153(5),T(³ H)=?220(6), andT(¹ G)=?79(4); for^168–166Er:z _4f =20.1(0.7),T(³ F)=?77(6),T(³ H)=?111(7), andT(¹ G) =?43(5). The normalization of these parameters with the corresponding nuclear parameters λ for both isotope pairs leads to almost identical parameter values indicating a dominant influence of the field shift effect in second-order for thez _4f parameter and in third-order for the parametersT(³ F),T(³ H), andT(¹ G).     

Experimental study on methods minimizing the influence of velocity-changing collisions in Doppler-free saturation spectroscopy

A method based on homodyne mixing is described which facilitates the use of rf-modulation of the pump beam for laser saturation spectroscopy together with conventional kHz lock-in amplifiers yielding a substantial reduction of disturbing pedestals present due to collisions in an atomic vapour. The technique benefits also from the significant improvement in the signal to noise ratio when transferring the Doppler-free signal to a frequency domain of several MHz where the interfering laser noise is low. These experimental procedures allow measurements of high quality saturated absorption spectra in vapour cells of otherwise unfavourable high gas pressure such as in commercial see-through hollow-cathodes. In addition we report the detection of an optogalvanic signal at rf-modulation (3.3 MHz).