Laser-rf Double Resonance Research Articles

CW-Dye Laser Spectrometer for Ultrahigh Resolution Spectroscopy: Design and Performance

This work is devoted to building-up of ultrahigh resolution cw-dye laser spectrometer system. This system used self-frequency-stabilized and temperature-compensated plano-confocal reference cavity. The one-way propagation is achieved using new construction of optical diode. The laser frequency selection and tuning is accomplished using Mach-Zehnder interferometer of free spectral range 42.5 GHz. In combination with computerized tunable radio frequency technique, this system is capable of a resolution of about ±1 KHz. Applications for measuring high lying, weakly occupied metastable states of free atoms (line 548.792 nm of V-51) are investigated to a high degree of accuracy. The results of the constants A and B of the hfs as measured by fluorescence spectroscopy show that A = 160.762 and B = -17.918, while the obtained results for the hfs constants A and B as measured by laser-RF double resonance technique give A = 160.9950 and B = -17.3358.

Precision measurement of laser RF double resonance spectra with an effective compensation of residual magnetic field

We have been developing a novel laser spectroscopy method-“OROCHI” for radioisotopes trapped in superfluid helium. This new method is expected to determine nuclear spins and moments of exotic nuclei by precise measurement of Zeeman and hyperfine splitting of atoms using laser double resonance method. Its feasibility has been confirmed by means of a series of experiments with various stable atoms in superfluid helium, while the accuracy of experimental results is found strongly affected by external magnetic field. In order to obtain reliable and accurate results for atomic spectra with “OROCHI” method, based on laser RF double resonance spectroscopy of on-line experiment, we performed off-line test experiments for \(^{85,87}\)Rb in helium buffer gas. In this test experiment, we used three mutually orthogonal coils to effectively compensate for laboratory residual magnetic field and subsequently observed precise laser RF double resonance spectra of atoms which affords us accurate nuclear spin value. By comparison of those results, we could make clear the effect of residual magnetic field on experimental results. The details of “OROCHI” method and test experiments are presented.

Investigation of the hyperfine structure of electronic levels in chromium atom

Measurements of the hyperfine structure (hfs) of electronic levels of the chromium atom were performed using two spectroscopic methods. For 7 energy levels (3 even parity and 4 odd parity) the magnetic dipole and electric quadrupole hyperfine interaction constants A and B were determined for the first time. In this case the method of laser induced fluorescence (LIF) on an atomic beam was used. The low lying metastable levels belonging to the term 3d44s2 a5D were remeasured by the method of laser-rf double resonance on an atomic beam (ABMR-LIRF). To improve the accuracy of hyperfine splittings measurements, the stability of the radio frequnecy (rf) generator was increased by the use of a frequency standard synchronized by a GPS signal. The values of the hfs intervals for these levels were determined with the accuracy of a few kHz. The improvement in accuracy enabled an estimation of the octupole-coupling constant C.

Novel nuclear laser spectroscopy method using superfluid helium for measurement of spins and moments of exotic nuclei

We have been developing a novel nuclear laser spectroscopy method “OROCHI” for determining spins and moments of exotic radioisotopes. In this method, we use superfluid helium as a stopping material of energetic radioisotope beams and then stopped radioisotope atoms are subjected to in situ laser spectroscopy in superfluid helium. To confirm the feasibility of this method for rare radioisotopes, we carried out a test experiment using a 85Rb beam. In this experiment, we have successfully measured the Zeeman resonance signals from the 85Rb atoms stopped in superfluid helium by laser-RF double resonance spectroscopy. This method is efficient for the measurement of spins and moments of more exotic nuclei.

Techniques of laser spectroscopy in investigations of lanthanides’ free atoms and ions

Various experimental methods, used in Chair of Quantum Engineering and Metrology for determination of the hyperfine structure of electronic levels in lanthanides atoms and ions, are presented. In turn the spectroscopic methods on an atomic beam (laser induced fluorescence and laser-rf double resonance ABMR-LIRF), laser-rf double resonance in a Paul trap and spectroscopic methods in a hollow cathode discharge (optogalvanic detection and laser induced fluorescence) are presented. Each method has been characterized with its potential accuracy and domain of application. The results achieved for the atoms and the ions of lanthanum, praseodymium, neodymium and europium have been published in numerous articles (compiled in the reference list).

High-Resolution Ultraviolet Laser Spectroscopy in Atomic Erbium

High-Resolution Ultraviolet Laser Spectroscopy in Atomic Erbium

High precision investigations of the hyperfine structure of metastable levels in a chromium atom

A series of precise measurements of the hyperfine structure (hfs) of nine metastable levels in a chromium atom 53Cr has been performed. For eight levels the hfs has been investigated with the method of laser induced fluorescence (LIF) on an atomic beam, and for the lowest-lying metastable level 3d54s 5S2 a still more precise method of laser-rf double resonance on an atomic beam (ABMR-LIRF) has been applied. A semi-empirical analysis of the fine and the hyperfine structure of the chromium atom, including many-body interaction effects, has been carried out in order to determine the value of the nuclear electric quadrupole moment, which amounts to Q = −0.22(1) barn.

Laser-Rf double-resonance measurements of the metastable 3 d 3 4 s 5 P 1,2,3 , 3 d 2 4 s 2 1 G 4 states of 47 Ti

The hyperfine structure (hfs) of 4 metastable states of 47Ti has been measured very precisely by a laser-rf double resonance method. The corresponding hyperfine structure constants Aexp and Bexp have supplied a set of experimental data necessary for hyperfine structure analysis and determination of Sternheimer free nuclear quadrupole moment Q.

Hyperfine-structure studies of Nb II: Experimental and relativistic configuration-interaction results.

We report an experimental and theoretical study of the hyperfine structure (hfs) in various metastable states in $^{93}\mathrm{Nb}$ ii. Hyperfine structures of five levels in Nb ii have been measured using a combination of the laser-rf double resonance and laser-induced fluorescence methods in a collinear laser--ion-beam geometry. Theoretically, for J=2, a multireference calculation of energies and hfs based on a relativistic configuration-interaction methodology of the lowest ten levels in the (4d+5s${)}^{4}$ manifold is reported. The average energy error is 450 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. Many of the hyperfine constants show large changes from the Dirac-Fock values and the magnetic dipole constant has a 4% accuracy for the one J=2 level measured. We have also identified all the core-valence and core-core effects that dominate the energy differences and hfs.

Laser-rf double-resonance study of SiO+

We used the laser-rf double resonance method to measure 15 fine structure intervals for rotational quantum numbers ranging from N = 5 to 79 of the ν = 0 level of the X2Σ+ state of SiO+. We present a molecular model, including perturbations from the A2Π state, which explains the observed strong variation of fine structure as a function of rotational quantum number. These data yield greatly improved predictions of the microwave spectrum of the ground state of SiO+. In particular we predicted the ground state rotational transition (N = 2, J = 5/2) → (N = 1, J = 3/2) to be 86 063(1) MHz, confirming that this transition is not the source of the radio line known as U86.2 at 86 243.45(40) MHz.

Precision measurement of the hyperfine structure and nuclear moments of 180mTa by laser-rf double resonance.

Hyperfine structure of the 5${\mathit{d}}^{3}$6${\mathit{s}}^{2}$ $^{4}$${\mathit{F}}_{3/2}$ ground state in $^{180\mathit{m}}\mathrm{Ta}$ i was precisely measured by means of atomic-beam laser-rf double-resonance spectroscopy. Hyperfine-interaction constants A and B for the ground state $^{4}$${\mathit{F}}_{3/2}$ were determined with accuracies of 3 and 10 ppm, respectively. The nuclear electric quadrupole moment was derived, as well as a precise value of the magnetic moment for $^{180\mathit{m}}\mathrm{Ta}$ (${\mathit{I}}^{\mathrm{\ensuremath{\pi}}}$=${9}^{\mathrm{\ensuremath{-}}}$): the magnetic dipole moment is ${\mathrm{\ensuremath{\mu}}}_{\mathit{I}}^{180\mathit{m}}$=+4.825(11)${\mathrm{\ensuremath{\mu}}}_{\mathit{N}}$ and the spectroscopic quadrupole moment is ${\mathit{Q}}_{\mathit{s}}^{180\mathit{m}}$=+4.946(20)b.

Hyperfine structure of high-L states in 143,145Nd I by atomic-beam laser-rf double resonance.

The atomic-beam laser-rf double-resonance technique has been used to study the hyperfine structure (hfs) of the metastable {sup 7}{ital L}{sub 5--11} and {sup 7}{ital K}{sub 4} states of the 4{ital f}{sup 4}5{ital d}6{ital s} configuration in {sup 143,145}Nd I. Four zero-field intervals were measured in each state and the results used to assign the conventional hfs constants {ital A} and {ital B}. Comparison of the results with predictions of the Sandars-Beck model allowed evaluation of the relevant single-electron radial hfs integrals. These are compared with earlier results from the Nd I atomic ground term and with extrapolations from other rare-earth elements. The unusually large orbital-angular-momentum values ({ital L}=7 and 8 for the states studied) do not appear to have introduced any anomalous effects. {ital Ab} {ital initio} calculations are not yet feasible for the complex 4{ital f}{sup 4}5{ital d}6{ital s} levels studied.

Hyperfine structure in the two lowest electronic states of PrO by molecular-beam laser-rf double resonance

The hyperfine structure (hfs) splittings in the electronic ground state ( Ω = 3.5 , v = 0) and the first excited electronic level (Energy = 220 cm −1, Ω = 4.5 , v = 0) of 141PrO have been measured over a broad range of J-values to a precision of about ±3 kHz. No perturbations are observed. The levels are represented as states of Pr(III) 4 f 26 s in an axial electric field, and the hyperfine structure resulting from the combined hfs and rotational Hamiltonians is worked out. The contribution due to the interaction between the two states of different Ω is found to be important. A single least-squares fit is made of the resulting theoretical expressions to the 166 radiofrequency (rf) measurements in the two states. Efforts are made to identify the contributions analogous to the conventional terms involving b, c, and eqQ. The perturbations in the optical spectra (of systems XVII and of the band at 6100 Å) are found to be in the common upper level (as previously reported), as is the Λ-doubling. The hyperfine structure of the upper state is determined to a precision of a few Mhz.

Hyperfine structure of the 4f75d26s 11F term of 155,157Gd I by laser-rf double resonance.

The atomic-beam laser-rf double-resonance method has been used to measure the hyperfine structure (hfs) of the J=2--8 levels of the $^{11}\mathrm{F}$ term of 4${f}^{7}$5${d}^{2}$6s in $^{155}$,157Gd. Results are also reported for the J=2,5 levels of the $^{7}\mathrm{D}$ term of 4${f}^{7}$5d6${s}^{2}$. Less precise hfs results are given for ten highly excited even-parity levels, and isotope shifts are given for 16 optical lines. L-S limit effective-operator expressions are given for the hfs A and B values of arbitrary states built from three open electron shells. When specialized to the $^{11}\mathrm{F}$ term in Gd i, these expressions reveal a marked perturbation between the J=5 levels of 4${f}^{7}$5${d}^{2}$6s $^{11}F$ and 4${f}^{7}$5d6${s}^{2}$ $^{7}D$. The perturbation can also be detected from the fine-structure intervals.

High-precision measurements of hyperfine structure in Tm II, N 2+ and Sc II

We have applied the technique of collinear fast-ion-beam laser spectroscopy to measure the hyperfine structure (hfs) in Sc II, Tm II and N 2 +. Laser-induced fluorescence was observed from a 50 keV ion beam which was superimposed with the output of an actively stabilized ring dye laser (rms bandwidth < 1 MHz). Hyperfine measurements were made in the metastable 3d 2 and the excited 3d4p configuration of Sc II and in the 4f 136s and 4f 135d configurations of Tm II. The fine and hyperfine structure of N 2 + has been observed in the (0, 1) and (1, 2) bands of B 2 Σ u + −X 2 Σ g + system. Higher-resolution measurements of the metastable 3d 2 configuration in Sc II were also made by laser-rf double resonance. The experimental results are compared with those obtained by multiconfiguration Dirac-Fock ab-initio calculations.

Stimulated resonance Raman spectroscopy: An alternative to laser-rf double resonance for ion spectroscopy.

Stimulated resonance Raman spectroscopy is presented as an alternative to laser-rf double resonance for obtaining high-precision measurements in ion beams. By use of a single-phase modulated laser beam to derive the two required fields, the laser-ion-beam alignment is significantly simplified. In addition, this method is especially useful in the low-frequency regime where the laser-rf double-resonance method encounters difficulties due to modifications of the ion-beam velocity distribution. These modifications, which result from interaction with the traveling rf wave used to induce magnetic dipole transitions, are observed and quantitatively modeled.

High-precision hyperfine structure measurement in slow atomic ion beams by collinear laser-rf double resonance

A new collinear laser-ion beam apparatus for slow ions (1–1.5 keV) has been built for measuring the hyperfine structure of metastable levels of ions with the laser-rf double resonance technique. Narrow linewidths of ~ 60 kHz (FWHM) have been observed for the first time in such systems. As a first application the hyperfine structure of the 4f 7( 8S o)5d 9D J o metastable levels of 151,153Eu + has been measured with high precision.

Standing-wave and intensity effects in intracavity laser RF double resonance spectroscopy

The laser and RF absorption spectra in a laser-RF double resonance configuration with the gas sample placed inside the laser cavity are exactly calculated by means of a semiclassical three-level model and interpreted through the dressed atom approach. Laser standing-wave effects and intensity effects are studied. Several kinds of nonlinear coherent phenomena are evidence. High-resolution spectroscopic applications are considered.

Fast beam collinear laser-rf double resonance

The method and application of fast beam collinear laser-rf double resonance are discussed. Following a short theoretical treatment of the collinear interaction of fast atoms with rf and laser fields, the experimental procedure and some technical details are presented. Selected applications of the method: (i) hyperfine structure and atomicg-factor measurements, and (ii) experimental studies of fundamental aspects of atom-field interactions, are described. prospective applications in nuclear physics experiments are discussed.

Hyperfine structure of 151,153Eu+ in the state 4f7(8So)5d 9D4o by collinear laser-rf double resonance.

An apparatus has been constructed for laser--radio-frequency double-resonance studies of very-low-energy-ion beams with collinear laser-ion geometry. The ion energy of only 1--2 keV leads to extremely narrow linewidths (\ensuremath{\sim}60 kHz). This paper describes measurements of the hyperfine structure of $^{151}\mathrm{Eu}^{+}$ and $^{153}\mathrm{Eu}^{+}$ in the level 4${f}^{7}$(${}^{8}$${S}^{o}$)5d ${}^{9}$${D}_{4}^{o}$. The hyperfine constants A and B have been determined with a much higher accuracy than before. The present values of these constants (in MHz) are =113.159(1), =-215.356(10), =-50.415(1), =-548.357(10). .AE