Optogalvanic Spectroscopy Research Articles

New energy levels of atomic holmium discovered by laser spectroscopy in the near infrared spectral range

A combination of optogalvanic spectroscopy and laser-induced fluorescence spectroscopy with a continuous wave tunable single mode Ti-Sa laser was applied to find new energy levels of atomic holmium. Free and excited holmium atoms were produced in a liquid nitrogen-cooled hollow-cathode lamp. In this study, we examined 35 spectral lines of Ho I in the near-infrared wavelength range from 698 nm to 833 nm. Altogether, 16 new energy levels have been discovered, 5 levels of even parity and 11 levels of odd parity. Another four energy levels have been discovered but have already been published by another research group. Data on the hyperfine structure for the new levels are presented. Additionally, hyperfine structure data of three known levels of even parity were determined for the first time. The existence of the new energy levels was confirmed by analyzing 60 lines of previously measured Fourier transform spectra to precisely determine the energy of the levels.

Comparison of Optogalvanic and Laser-Induced Fluorescence Spectroscopy

When investigating complex atomic spectra, it may happen accidentally that two or even several transitions between different pairs of combining energy levels have nearly the same wavenumber, and the observed spectral lines are overlapping (blend situations). In such cases, investigations of hyperfine structures can be very helpful in the identification of the involved transitions. In this paper, two complicated blend situations within the spectra of lanthanide atoms (Praseodymium and Lanthanum) are discussed as examples. The experimental methods applied are optogalvanic and laser-induced fluorescence spectroscopy, combined with emission spectra gained via Fourier transform spectroscopy. It is shown that, in such cases, a combination of optogalvanic and laser-induced fluorescence detection is necessary to find all transitions contributing to the observed spectral signatures.

Laser optogalvanic spectroscopy of lead lines — Isotope shifts and hyperfine structure studies

Six atomic lines of Pb I in the 569–612 nm wavelength range and two lines of Pb II in the wavelength range of 560-608 nm were examined using optogalvanic spectroscopy. A hollow cathode discharge lamp was the source of Pb atoms and ions. Hyperfine structure constants were measured for levels associated with the observed transitions. The result of the research was also the determination of isotope shifts in the studied lines. The experimental data we have obtained complement or correct the existing database. We determined six values of the A constants of the hyperfine structure of Pb I, including one value determined for the first time and clarified one value of the A constant for Pb II. We determined seven new values of isotopic shifts between individual isotopes for two Pb I lines and one Pb II line. Furthermore, ab-initio MCDHF calculations of the observed isotope shifts and hyperfine structure constants were performed. Theoretical results are in good agreement with experimental data.

New even parity fine structure energy levels of atomic vanadium

Four new fine structure energy levels of atomic vanadium have been discovered for the first time. Experiments were carried out with laser-induced fluorescence spectroscopy and optogalvanic spectroscopy using tunable continuous wave lasers in the wavelength ranges between 750 nm and 850 nm and between 590 nm and 650 nm, respectively. The new levels, all lying in the 42 400 to 49 940 cm−1 energy range, were each experimentally confirmed by two or more observed transitions involving previously known energy levels. Accurate energy level values were found using lines measured by Fourier transform spectroscopy. The values for the total angular momentum quantum numbers J of the new levels were found by the analysis of the hyperfine structure of the spectral lines investigated. Magnetic dipole hyperfine structure constants A for all new levels were determined. Additionally, for one previously known energy level the magnetic dipole hyperfine structure constant A from the literature was corrected.

Dysprosium optogalvanic spectroscopy in a hollow cathode lamp

This work presents data obtained from optogalvanic spectroscopy (OGS) of dysprosium (Dy) using a commercial hollow cathode lamp. Combining laser beams from two tunable dye lasers, it was possible to identify 13 electronic transitions from excited states of the atom not observed or registered in published papers and the NIST database; these lines were observed between 555–575 nm and 585–615 nm. The study of 13 two-step transitions found in this work complement the available data for the Dy which may support other research or any work using this atom.

The effect of saturation on hyperfine and Zeeman spectra in laser absorption spectroscopy

Using laser absorption spectroscopy, i.e. techniques such as optogalvanic spectroscopy or laser-induced fluorescence, it is often possible to separate and register individual components of a hyperfine or Zeeman structure. If these components are well separated (i.e. the distances between them are greater than their FWHM), it is relatively easy to determine their frequency position. However, when the atomic structure is very rich and the individual components overlap, problems arise with the correct determination of the position of the respective intensity peaks. Usually, only the envelope curve can be fitted to the observed structure, hence assumptions about the relative intensity ratios of the overlapping components as well as assumption about the line profile of a single component are necessary. An additional problem is the saturation effect. The saturation effect changes the theoretically predicted relative intensity ratios between the line components. In the current work, we present a method of analyzing experimentally observed hyperfine structure (hfs) patterns without and with an external magnetic field (Zeeman-hfs), which considers the saturation effect and allows for a relatively precise determination of the position of the individual components. In addition, we point out that, because of the saturation effect, hyperfine structure measurements should be carried out in conditions where the polarization of the exciting light (relative to magnetic stray fields) is known and this fact should be reflected in computer simulations which adjust a model function based on theoretical predictions to the experimental spectrum.

High stability multiple-frequency cavity locking based on Doppler-free optogalvanic Calcium ion spectroscopy.

Doppler-free spectroscopy of 40Ca+ on the transition 3D3/2 → 4P1/2 known as the frequency standard for repumping beam of Calcium ion trap was performed by means of optogalvanic detection. This reference signal was applied to measure the frequency stability of laser locked to the resonance of an ultra-low expansion (ULE) glass made cavity. Lamb dip spectrum fitting of this Calcium ion spectra revealed that the long-term drift of our laser system is below 2 MHz per hour. A simple setup for frequency locking of dual colour of lasers at 866 nm and 780 nm was also demonstrated. Consistencies of the frequency difference between these two lasers were measured less than 2 MHz in a hour after stabilizing both lasers to the cavity.

Odd-parity autoionizing levels of uranium observed by two-color two-step photoionization optogalvanic spectroscopy

Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels with the first-step laser and by scanning the second-step laser wavelengths. By blocking the first-step laser, single-color, two-photon ionization transitions were also identified. From these results, we have found more than 50 odd-parity autoionizing levels of uranium in the energy, ranging from the ionization potential (49958.4 cm−1) to 51 150 cm−1. The determined energy levels are within ∼±1 cm−1 of previously reported values.

Optogalvanic spectroscopy of the Zeeman structure of argon energy levels close to the ionization limit

The Lande gJ factors for high lying states of the argon atom by laser optogalvanic spectroscopy were measured, in most cases with an uncertainty of less than 0.005. The Zeeman structure of 12 argon lines with wavelengths in the range 598.7-612.8 nm was investigated. We determined Lande gJ factors for 9 odd parity levels and verified the data for several other levels.

Simultaneous intermodulated optogalvanic spectroscopy and laser induced fluorescence in an erbium hollow cathode lamp

In this work we propose an experimental apparatus to investigate the isotope shift using two sub-Doppler techniques: Intermodulated Laser Induced Fluorescence and Intermodulated Optogalvanic Spectroscopy. The experimental set uses a portable hollow cathode lamp, which is an atomic source less expensive and simpler when compared to other techniques e.g. atomic beam. The method was applied to the erbium rare earth, being possible to observe the isotope shift for three transitions from the ground state: 0 → 17,347.860 cm−1 (576.440 nm), 0 → 17,157.307 cm−1 (582.842 nm) and 0 → 17,073.800 cm−1 (585.695 nm). The experimental erbium data from the literature were used to perform simulations of spectra in order to compare and confirm the accuracy of our measurements.

On the Time Resolved Optogalvanic Spectroscopy of Neon in a Hollow Cathode Discharge

On the Time Resolved Optogalvanic Spectroscopy of Neon in a Hollow Cathode Discharge

Investigation of the Zeeman—hyperfine structure of atomic niobium

Laser spectroscopy was used for the investigation of the Zeeman-hf structure of 22 lines of atomic niobium in the visible region between 573.7 and 649.4 nm. We used two methods of laser absorption spectroscopy: laser induced fluorescence (LIF) method and optogalvanic spectroscopy (OG). The source of niobium atoms was a hollow cathode discharge tube. The magnetic field of approximately 800 G was generated by a permanent neodymium magnet. We determined experimentally for the first time the Lande gJ factors for 10 levels. We also verified earlier experimental data on the hf structure as well as data from the NIST database regarding Lande gJ factors.

New energy levels of atomic lanthanum with small total angular momentum quantum number discovered by laser spectroscopic methods in the near IR

Optogalvanic spectroscopy as well as laser-induced fluorescence spectroscopy were applied in order to find new energy levels of atomic lanthanum. A hollow-cathode lamp and a tuneable continuous wave titanium-sapphire laser in the wavelength range from 750 nm to 850 nm were used for the measurements. Three energy levels of even parity with small values of total angular momentum quantum number J were discovered: 38 519.18 cm−1with J=1/2,40 392.80 cm−1with J=3/2,and 42 191.24 cm−1with J=3/2. The existence of these three levels was confirmed by laser excitations of several spectral lines as well as by spectral lines from a Fourier transform spectrum. Magnetic dipole hyperfine structure constants of the three new levels were determined from fits of the experimental spectra of the laser lines.

Laser spectroscopic investigation of atomic holmium in the wavelength range from 780 nm to 830 nm: Hyperfine structure measurements and a new energy level

The hyperfine structure of neutral holmium was studied using a hollow cathode discharge lamp and laser-induced fluorescence spectroscopy or optogalvanic spectroscopy, respectively. Altogether 42 spectral lines in the wavelength range from 780 nm to 830 nm were investigated. Magnetic dipole hyperfine structure constants A and electric quadrupole hyperfine structure constants B were determined for 23 levels of even parity and for 25 levels of odd parity. Eight of the reported hyperfine structure constants have not been published before. For most other levels, previously published hyperfine structure constants have been measured with greater precision. Additionally, one new energy level 29013.43 cm−1 with odd parity and J=13/2 has been discovered.

Intracavity optogalvanic detection of 14C using a stabilized 14CO2 laser

Intracavity optogalvanic detection of 14C utilizes the narrow band specificity of 14CO2 laser resonances in the infrared spectrum, coupled with greatly enhanced sensitivity from amplified effective path lengths in optical cavities. Background (nonresonant) interactions are also enhanced in such cavities, making proper separation of signals from background imperative. Intracavity Optogalvanic Spectroscopy (ICOGS) is similar to cavity ring-down spectroscopy (CRDS) with certain crucial differences. An ICOGS model, based on a basic CO2 laser and optogalvanic effect physics, is presented. Experimental results using a laboratory instrument with a continuous flow of small CO2 samples in a buffer gas illustrate the model. It is shown that acquisition of optimized signal-to-background ratios for the quantitation of 14CO2 in samples of order 10 μg is achievable, considerably smaller than with CRDS.

Laser-based radiocarbon detection in the laboratory: How soon?

Research over the past 25 years and the use of accelerator mass spectrometry (AMS) have demonstrated benefits of single-atom counting of 14 C compared with scintillation monitoring of 14 C radioactive decay for a multitude of applications in drug development studies. These include pharmacokinetics and metabolism studies, microdosing studies, and quantification of DNA adducts. In the last decade, the possibility of single-atom counting using lasers has been demonstrated, providing the possibility of simplified laboratory-based systems, which can equal or excel AMS sensitivity and provide scintillation system convenience without high levels of radioactivity. To achieve the required sensitivity, optical storage cavities have been used to enhance the laser interaction of the low densities of radiocarbon present. Two types of laser technologies have been used-cavity ring-down spectroscopy (CRDS) and intracavity opto-galvanic spectroscopy (ICOGS). Problems to be overcome to achieve routine use have included separation of the 14 C signal from backgrounds, achievement of acceptable precision and accuracy, reduction of measurement times for small samples, and improvement in the ease of use for the operator. Both technologies have achieved impressive results to date using samples of order 1 mg with CRDS and 10 μg with ICOGS. Commercial development is the next step.

MCDHF calculations of isotope shifts in neutral antimony

Ab initio multiconfiguration Dirac–Hartree–Fock (MCDHF) calculations have been carried out in order to determine the isotope shift (IS) electronic parameters of transitions belonging to electric dipole (E1) transition arrays 5s25p3−5s25p26s,5s25p26s−5s25p26p and 5s25p26s−5s25p27p in neutral antimony, Sb I. In a correlation model limited to single and double excitations from the valence shells, these parameters, combined with the changes in mean-square nuclear charge radius δ⟨r2⟩123,121 compiled by Angeli and Marinova [3] produce isotope shifts values in good agreement with the most recent measurements by high-resolution emission and optogalvanic absorption spectroscopy of Sobolewski et al. [5] but not with the old measurements of Buchholz et al. [4] for 5p3−5p26s. However, our analysis does not allow to reject the latter due to the large uncertainty affecting δ⟨r2⟩123,121, i.e. 0.072 ± 0.048 fm2 [3]. This shows the need of a more accurate determination of this nuclear parameter. Although improving excitation energies, the inclusion of core-valence correlation limited to one hole in the 4d core subshell destroyed the theory-experiment agreement on the IS parameters.

Experimental study of the electric field in a hollow cathode discharge in hydrogen: influence of sputtering

Doppler-free two photon optogalvanic spectroscopy was employed in extensive studies to measure the electric field strength in the cathode fall region of a hollow cathode discharge (HCD), operated in pure hydrogen, via the Stark splitting of the 2S level of atomic hydrogen. The high quality measurements, based on an improved cathode design and laser spectroscopic set-up, reveal clear differences in the recorded spectra obtained for different cathode material (stainless steel and tungsten) at otherwise identical discharge conditions. It is well known, that the sputtering rate of tungsten is about four orders of magnitude less compared to stainless steel; hence the hydrogen plasma in front of the stainless steel cathode is much more contaminated by iron compared to tungsten. This study is focussed on analyzing the distortion of the spectra, i.e. the corresponding local electric field strength, depending on cathode material and laser power. We refer the more pronounced distortion of the spectra in case of a stainless steel cathode to the related large contamination of the hydrogen plasma due to atomic iron which is also expanding into the central discharge. Spectra recorded for different laser power, i.e. different spectral irradiance, allow verifying spectroscopic conditions, where the distortion of the spectra becomes quite negligible even for stainless steel cathode.

Measured cathode fall characteristics depending on the diameter of a hydrogen hollow cathode discharge

In this work, Doppler-free two photon optogalvanic spectroscopy is used to measure the electric field strength in the cathode fall region of a hollow cathode discharge, operated in pure hydrogen, via the Stark splitting of the 2S level of atomic hydrogen. The cathode fall characteristics are analysed for various pressures and in a wide range of discharge currents. Tungsten is used as the cathode material, because it allows for reliable measurements in a fairly wide range of discharge conditions and because of its minimal sputtering. Two cathode diameters (10 mm and 15 mm) are used to study the dependence of the cathode fall on discharge geometry. The measurements reveal that the cathode fall characteristics are quite independent on the cathode diameter for equal cathode current density; hence the measurements can be used to test one dimensional modelling of the cathode fall region for low pressure hydrogen discharges using e.g. plane parallel electrodes.

Optogalvanic spectroscopy of the hyperfine structure of the 5p65d 2D3/2,5/2 and 5p64f 2F5/2,7/2o levels of La iii

We measure the hyperfine structure of the $5p^65d$ ${}^2D_{3/2}$, $5p^65d$ ${}^2D_{5/2}$, $5p^64f$ ${}^2F^o_{5/2}$, and $5p^64f$ ${}^2F^o_{7/2}$ levels in doubly-ionized lanthanum (La III; La$^{2+}$) in a hollow cathode lamp using optogalvanic spectroscopy. Analysis of the observed spectra allows us to determine the hyperfine $A$ coefficients for these levels to be $A_{D3/2}=412(4)$ MHz, $A_{D5/2}=20(5)$ MHz, $A_{F5/2}=319(2)$ MHz, and $A_{F7/2}=155(4)$ MHz; and provide estimates for the hyperfine $B$ coefficients as $B_{D3/2}=105(29)$ MHz, $B_{D5/2}=157(40)$ MHz, $B_{F5/2}=-2(53)$ MHz, and $B_{F7/2}=171(51)$ MHz.