Atomic Thallium Research Articles

Measurement of the electric quadrupole amplitude in atomic thallium transition using electromagnetically induced transparency

We report on a measurement of the transition amplitude ratio χ of an electric quadrupole () to a magnetic dipole () of the transition in atomic thallium. We utilized the electromagnetically induced transparency mechanism and the sideband-bridging technique to resolve the isotopic transitions and their hyperfine manifold. Our measurement gave for 205Tl, and for 203Tl, which was measured for the first time. Our results provide a reference point for the theoretical calculation of atomic structures, and new input for the long dispute on the atomic thallium parity non-conservation measurements.

P , T -Violating and Magnetic Hyperfine Interactions in Atomic Thallium

We present state-of-the-art string-based relativistic general-excitation-rank configuration interaction and coupled cluster calculations of the electron electric dipole moment, the nucleon–electron scalar-pseudoscalar, and the magnetic hyperfine interaction constants ( α d e , α C S , A | | , respectively) for the thallium atomic ground state 2 P 1 / 2 . Our present best values are α d e = − 558 ± 28 , α C S = 6.77 ± 0.34 [ 10 − 18 e cm], and A | | = 21172 ± 1059 [MHz]. The central value of the latter constant agrees with the experimental result to within 0.7% and serves as a measurable probe of the P , T -violating interaction constants. Our findings lead to a significant reduction of the theoretical uncertainties for P , T -odd interaction constants for atomic thallium but not to stronger constraints on the electron electric dipole moment, d e , or the nucleon–electron scalar-pseudoscalar coupling constant, C S .

Tunable frequency-stabilization of an ultraviolet laser using a hollow-cathode lamp of atomic thallium

A frequency-stabilized ultraviolet laser system, locked to the thallium resonant transition at 377.5 nm, was demonstrated using a novel bichromatic spectroscopy technique for tuning the zero-crossing laser-lock point. The 377.5 nm 6P1/2→7S1/2 transition is important for thallium laser cooling and trapping experiments. The pressure shift, owing to the high pressure buffer gas of the hollow-cathode lamp, was observed using an atomic beam resonance as the reference. Such a shift was corrected by adjusting the peak ratio of the two Doppler-free saturation profiles that resulted from the two pumping beams with a 130 MHz frequency difference. The resulting frequency stability of the ultraviolet laser was 0.5 MHz at a 0.1 s integration time. This scheme is compact and versatile for stabilizing laser systems, which require a sub-megahertz stability and frequency tunability.

Absolute frequency measurements of the molecular iodine hyperfine transitions at 535 nm

We report absolute frequency measurements of the a1, a10, and a15 hyperfine components of molecular iodine P(28) 30-0 line at 535 nm. A frequency-doubled 1070 nm Nd:GdVO4 laser is frequency stabilized to a hyperfine component of I2 using the third-harmonic demodulation technique. The frequency stability of 3×10−12 is achieved at 10 s averaging time when its frequency is stabilized to the a1 component. An optical frequency comb is used to measure its absolute frequency. The pressure shift is investigated to obtain the absolute frequency at zero pressure. The effect of pressure and power broadening of the a10 component are also investigated. This light source can be used for investigating parity nonconservation effect in atomic thallium.

Single frequency 1070 nm Nd:GdVO_4 laser using a volume Bragg grating

We demonstrate a single frequency diode-pumped Nd:GdVO(4) laser at 1070 nm using a volume Bragg grating as the output coupler of a short plano-concave cavity. The TEM(00) output had a maximum power of 300 mW and a linewidth less than 23 MHz. The beam propagation parameter M2 and the divergence angle at 200 mW were 1.2 and 0.37°, respectively. The single frequency tuning range was 5.1 GHz at 100 mW. Upon locking the laser frequency to a confocal reference cavity, a relative stability of 7.58 kHz was achieved. If frequency doubled, such as using a periodically-poled lithium niobate (PPLN) crystal, this laser offers an excellent light source for parity non-conservation experiments of atomic thallium.

Prospects of laser cooling in atomic thallium

One of the most precisely determined upper limits for the electron electric dipole moment (EDM) is set by the thallium (Tl) atomic beam experiment. One way to enhance the sensitivity of the atomic beam setup is to laser cool the Tl atoms to reduce the EDM-like phase caused by the E$\ifmmode\times\else\texttimes\fi{}$v effect. In this report, a cooling scheme based on the $6{P}_{3/2}(F=2)\ensuremath{\leftrightarrow}6{D}_{5/2}({F}^{\ensuremath{'}}=3)$ transition in Tl is proposed. The absolute frequency measurement of this nearly closed-cycle transition was performed in an atomic beam apparatus. Two Ti:sapphire lasers were frequency-doubled using enhancement cavities in X-type configurations to provide the needed 377- and 352-nm light sources for the optical pumping and cooling transitions, respectively. The absolute frequency of this cooling transition is determined to be 851 634 646(56) MHz.

ChemInform Abstract: Infrared (0.9-1.65 μm) Emission from Thallium Iodide Photoexcited with Ultraviolet Excimer Laser Radiation

The infrared emission spectra from 0.9 to 1.65 μm produced when thallium iodide vapor is photodissociated by excimer laser wavelengths of 193, 248, 308, and 351 nm are reported. In this spectral region, only atomic thallium transitions were observed. No emission from metastable atomic iodine at 1.315 μm (5 2P1/2→5 2P3/2) or thallium at 1.283 μm (6 2P3/2→6 2P1/2) was ever detected in contrast to strong 1.315 μm signals obtained by ultraviolet (UV) excimer laser dissociation of C3F7I. The failure to detect metastable atomic emission from TlI photodissociation is explained by the fast quenching of the metastable states during superelastic collision with electrons produced by photoionization of the TlI. Consequently, a pulsed iodine 1.315 μm laser based on photodissociation of thallium iodide does not seem practical.

Two-color three-photon excitation studies of thallium Rydberg states

We present new data on the even-parity Rydberg states of atomic thallium using two-step three-photon laser excitation technique in conjunction with a thermionic diode ion detector. Atoms are excited from the 6p 2P 1/2 ground state to the 7p 2P 1/2 intermediate state via two-photon excitation and subsequently promoted to the high lying ns 2 S 1/2 and nd 2D 3/2 Rydberg states. The first ionization potential of thallium is determined as 49,266.66(1) cm –1 using data for the ns 2 S 1/2 (25 ≤ n ≤ 54) and nd 2D 3/2 (24 ≤ n ≤ 65) Rydberg series. This value is believed to be more accurate because the contribution due to the hyperfine structure splitting of the 7p 2P 1/2 state (0.07185 cm –1) is much smaller as compared to that of the 6p 2P 1/2 ground state (0.711 cm –1).

Selective excitation of the 62 D 3/2 state of the atomic thallium beam

The absorption of the tunable narrow-band laser radiation with λ = 276.9 nm at the 62P1/2 → 62D3/2 transition in the atomic thallium beam is experimentally studied. The isotopic selectivity and efficiency of the excitation of the 62D3/2 state is investigated. The splittings between the 203Tl and 205Tl isotopes were found to be Δv = 0.98 and 1.25 GHz for the transitions with the nuclear momenta F = 1 → F = 1, 2 and F = 0 → F = 1, respectively, which is sufficient for a relatively high isotopic selectivity of the 62D3/2 state excitation with the subsequent ionization for the laser separation of the thallium isotopes. The effects that lead to the broadening of the resonance and a decrease in the selectivity are analyzed. The main contribution is related to the field broadening by the laser radiation, which limits the mean laser power density.

Atomic electric-dipole moments from Higgs-boson-mediated interactions

Electric-dipole moments of paramagnetic atoms can provide important insights into a unique kind of CP violation involving Higgs-boson-mediated interactions between leptons and hadrons. We report a limit for the coupling constant of such an interaction by combining the results of our relativistic many-body calculations and experimental data on the electric-dipole moment of atomic thallium. The importance of electron correlation in determining this limit is highlighted and its significance in the context of particle physics and cosmology is pointed out.

Three-photon resonance enhanced excitation spectrum of atomic thallium

We present first measurements on the resonance enhanced three-photon excitation in thallium, using a Nd:YAG laser pumped dye laser in conjunction with a thermionic diode ion detector. The even-parity 6s2ns2S1/2 (15⩽n⩽31) and nd 2D5/2 (13⩽n⩽42) Rydberg states have been observed. The measured level energies reveal a dynamic shift from the photoabsorption values, which is decreasing with increasing n, while the asymmetry in the line profile is observed to be increasing with increasing n. In addition, an autoionising level (sp24P3/2) adjacent to the ionization threshold has been observed and quantitatively analyzed using the Fano’s photoionization cross-section relation for an isolated autoionising resonance.

Resonance enhanced multi-photon excitation spectroscopy of atomic thallium

We present new data on the high Rydberg states of thallium using the resonance enhanced multi-photon excitation and ionization techniques in conjunction with a thermionic diode ion detector. The Rydberg states 6 s 2 n p 2 P 1/2 (7⩽ n⩽29), 6 s 2 n p 2 P 3/2 (7⩽ n⩽35) and 6 s 2 n f 2 F 5/2 (5⩽ n⩽48) have been observed via two-photon excitation from the ground state. The 6 s 2 n p 2 P 1/2,3/2 multiples due to spin–orbit interaction are resolved up to n=29. The observed energy separations among the multiplets are in excellent agreement to the calculated values using the valence electron model. The 6 s 2 n f 2 F 5/2 series have been observed up to n=48 for the first time. The first ionization potential of thallium has been derived as 49266.5(1) cm −1 which is in good agreement to the earlier work.

An interferometric test of time reversal invariance inatoms

The phase dependence of the photon momentum vector k and thedirection of an applied electric field E, which is asignature for an atomic T-odd interaction, is investigated for thefirst time using a fibre interferometer. Atomic thallium vapoursits in one arm of the interferometer and is subjected to laserradiation tuned near to the 6p1/2-6p3/2 transition at1281 nm. The results show no evidence of a k · Eeffect down to the level of 0.06±0.1 µrad for a field of10 000 V m-1. This sets a limit on the T-odd admixturecoefficient δT = (±0.9±2)×10-3. Someimportant sources of systematic effects are discussed as well as thefactors which limit the present sensitivity.

Study on the Solidification Process of Hgtl Amalgam at 30 at.% T

By means of a toroidal oscillating viscometer, logarithmic decrements of dampings have been measured in presence or absence of HgTl amalgam at 30 atomic percent thallium, at different temperatures, ranging from 12°C to 23°C.

Measurement of the electric quadrupole amplitude within the 1283-nm6P1/2−6P3/2transition in atomic thallium

We have measured the ratio of the electric quadrupole $(E2)$ to magnetic dipole $(M1)$ transition amplitude within the ${6P}_{1/2}\ensuremath{\rightarrow}{6P}_{3/2}$ transition in atomic thallium. Defining $\ensuremath{\chi}$ to be this $E2$ to $M1$ amplitude ratio, we find that $\ensuremath{\chi}=0.2387(10)(38)$, where the first error is statistical and the second represents a combined systematic error. In addition to providing a stringent test of theoretical wave-function calculations in thallium, accurate knowledge of this quantity is essential for existing and future measurements of parity nonconserving optical rotation on this same 1283-nm line in thallium.

Hg Amalgams are Homogeneous Compounds Having Liquid Metal Properties

By means of a toroidal oscillating viscometer, logarithmic decrements of dampings have been measured in presence of HgT1 amalgam at 28.1 atomic percent thallium, at different temperatures, ranging from 12,5°C to 17°C, with fluctuations every 0.25°C. In addition, the solidification process of Hgln amalgam has been investigated.

Rare-gas-induced broadening and shift of two-photon transitions to intermediate $\mathsf{(n=9{-}14)}$ Rydberg states of atomic thallium *

Results of broadening and shift measurements of Doppler-free two-photon lines for transitions from the ground state to the \(\) Rydberg states with intermediate principle quantum numbers of atomic thallium perturbed by rare gases are reported. The rates show a distinct behaviour in this range of principle quantum numbers and significant dependence on the total angular momentum of the upper nP state. The experimental results are compared with calculations using a Van der Waals potential and a superposition of polarization and Fermi potentials. Additionally, broadening and shift rates of the transition Tl 6P3/2-9P3/2 have been measured for quadrupolar as well as for mainly scalar excitation. The rates for both kinds of excitation coincide within the limits of error reflecting the small perturbation of the 6P3/2 state compared to that of the upper 9P3/2 state.

Magneto-optic rotation for an arbitrary field direction

We give a theory of magneto-optic rotation and pseudorotation spectra for forbidden transitions. The case considered is that of a weak magnetic field at an arbitrary angle to the direction of light of low intensity passing through a dilate atomic vapour. The theory is applied to the 1279 nm M1 transition in atomic lead and the 1283 nm M1/E2 transition in atomic thallium. Experimental Voigt and Faraday effect data for lead measured in a sensitive optical polarimeter provide confirmation of the predicted profiles.

Precise Measurement of Parity Nonconserving Optical Rotation in Atomic Thallium

We report a new measurement of parity nonconserving (PNC) optical rotation on the ${6p}_{1/2}$- ${6p}_{3/2}$ transition in atomic thallium near 1283 nm. The result expressed in terms of the quantity $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{Im}{{E1}^{\mathrm{PNC}}/M1}$ is $\ensuremath{-}(15.68\ifmmode\pm\else\textpm\fi{}0.45)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, and is consistent with current calculations based on the standard model. In addition, limits have been set on the much smaller nuclear spin-dependent rotation amplitude at ${R}_{S}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(0.04\ifmmode\pm\else\textpm\fi{}0.20)\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}8}$; this is consistent with theoretical estimates which include a nuclear anapole contribution.

Precise Test of Electroweak Theory from a New Measurement of Parity Nonconservation in Atomic Thallium.

We report a new measurement of parity nonconserving (PNC) optical rotation near the 1.28 $\ensuremath{\mu}$m, ${6P}_{1/2}\ensuremath{\rightarrow}{6P}_{3/2}$ magnetic dipole transition in thallium. We find the ratio of the PNC $E1$ amplitude to the $M1$ amplitude to be $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(\ensuremath{-}14.68\ifmmode\pm\else\textpm\fi{}0.17)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, which within the present uncertainty of atomic theory yields the thallium weak charge ${Q}_{w}(^{205}T\mathrm{l})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}114.2\ifmmode\pm\else\textpm\fi{}3.8$ and the electroweak parameter $S\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}2.2\ifmmode\pm\else\textpm\fi{}3.0$. Separate measurements on the $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ and $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ ground-state hyperfine components of the transition yield ${R}_{1}\ensuremath{-}{R}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(0.15\ifmmode\pm\else\textpm\fi{}0.20)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, which limits the size of nuclear spin-dependent PNC in Tl.