Isotopic shift in the3P1-3P0 Mg transition

High precision frequency measurements of the³ P ₁-³ P ₀ transitions have been performed for the three natural abundant Mg-isotopes in a metastable atomic beam. A second order hyperfine theory for two-electron atoms allows the determination of the centre-of-gravity for²⁵Mg and then the evaluation of the isotopic shift displacements. The high resolution frequency measurements (10^?8) show a noticeable departure of the total shift from a linear dependence with respect to the atomic mass.     

Isotopic shift measurement of the 3P1-3P0 fine structure transition of 24Mg and 26Mg

The isotopic frequency shift for the ³P₁-³P₀Δm_j=0 fine structure transition in the first metastable triplet of ²⁴Mg and ²⁶Mg is reported. The transitions corresponding to the two even isotopes of Mg have been observed via the fluorescence emission at 4571 Å of the intercombination line ³P₁-¹P₀ in a metastable atomic beam. The center frequencies have been measured with an uncertainty of 7×10^-9; the isotopic shift turned out to be 1706 ± 2 kHz.     

Ellipsometric measurement of magnetooptical nonreciprocal effects

To detect small rotation rates with a ring laser the two counter-propagating beams must be uncoupled. This lock-off can be realized using nonreciprocal optical effects yielding different optical path lengths for the two waves. Usually magnetooptical effects are employed for nonreciprocity. To measure, instead of calculating from optical constants, the magnitude of this nonreciprocal effects an ellipsometric method is proposed. Lock-off elements using Faraday or Kerr effect (polar and transverse, respectively) are treated. First measurements were made on FeNi films.     

Frequency measurement, isotope shift and hyperfine structure of the transition in atomic silver

The frequency of the centroid of the transition in Ag I has been determined by laser spectroscopy of a collimated metastable thermal atomic beam. We find MHz. The isotope shift MHz. For the magnetic hyperfine structure constant of the state, assuming IJ coupling, we find, MHz and MHz. Received 16 July 1999 and Received in final form 7 October 1999     

Spectroscopy of the 1S0-3P0 clock transition of 87Sr in an optical lattice

We report on the spectroscopy of the 5s(2) 1S0(F=9/2)-->5s5p 3P0(F=9/2) clock transition of 87Sr atoms (natural linewidth of 1 mHz) trapped in a one-dimensional optical lattice. Recoilless transitions with a linewidth of 0.7 kHz as well as the vibrational structure of the lattice potential were observed. By investigating the wavelength dependence of the carrier linewidth, we determined the magic wavelength, where the light shift in the clock transition vanishes, to be 813.5+/-0.9 nm.     

Observation and absolute frequency measurements of the 1S0-3P0 optical clock transition in neutral ytterbium

We report the direct excitation of the highly forbidden (6s2) 1S0 <--> (6s6p) 3P0 optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at approximately 70 microK in a magneto-optical trap. The measured frequency in 171Yb (F=1/2) is 518,295,836,591.6 +/- 4.4 kHz. The measured frequency in 173Yb (F=5/2) is 518,294,576,847.6 +/- 4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10(6)-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be approximately 10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.     

Observation of the 1S0-3P0 transition in atomic ytterbium for optical clocks and qubit arrays

We report an observation of the weak 6 1S0-6 3P0 transition in (171,173)Yb as an important step to establishing Yb as a primary candidate for future optical frequency standards, and to open up a new approach for qubits using the 1S0 and 3P0 states of Yb atoms in an optical lattice.     

Quantum interference effects in a multi-driven transition Fg = 3 ↔ Fe = 2

We calculated and studied the quantum coherence effects of a degenerate transition F_g = 3 ↔ F_e = 2 system interacting with a weak linearly polarized (with σ_± components) probe light and a strong linearly polarized (with σ_± components) coupling field. Due to the competition between the drive Rabi frequency and the Zeeman splitting, electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) are appeared at the different values of applied magnetic field in both cases that the Zeeman splitting of excited state Δe is smaller than the Zeeman splitting of ground state Δg (i.e., Δe < Δg) and Δe > Δg. It is shown that the resonance is broader and contrasts are higher for Δe < Δg than that for Δe > Δg at the same Rabi frequencies of probe and coupling fields.     

Doppler-free spectroscopy of the 1S0-3P0 optical clock transition in laser-cooled fermionic isotopes of neutral mercury

We report direct laser spectroscopy of the 1S0-3P0 transition at 265.6 nm in fermionic isotopes of neutral mercury in a magneto-optical trap. Measurements of the frequency against the LNE-SYRTE primary reference using an optical frequency comb yield 1 128 575 290 808.4+/-5.6 kHz in 199Hg and 1 128 569 561 139.6+/-5.3 kHz in 201Hg. The uncertainty, allowed by the observation of the Doppler-free recoil doublet, is 4 orders of magnitude lower than previous indirect determinations. Mercury is a promising candidate for future optical lattice clocks due to its low sensitivity to blackbody radiation.     

Angular distributions of atoms sputtered from NiAl{1 1 0} and Ni{1 0 0}

Using the laser post-ionization surface analysis technique, I have for the first time studied angular distributions of Ni and Al atoms sputtered from NiAl{1 1 0}. Emission angular distributions from Ni{1 0 0} have also been measured. I have observed preferential emissions of Ni and Al atoms along 〈1 1 1〉 and 〈1 0 0〉crystallographic directions for NiAl{1 1 0} and of Ni atoms along 〈1 1 0〉 and 〈1 0 0〉 directions for Ni{1 0 0}. The observed preferential ejections can be explained in terms of the theory of focusing-collision sequences. Because of the difference in surface binding energy between Al and Ni atoms, preferential ejection angles of Ni atoms are slightly different from those of Al atoms along the 〈1 1 1〉 ejections. For NiAl, the 〈1 1 1〉 preferential ejections were less prominent than the 〈1 0 0〉 preferential ejections and this can be related to the low efficiency of momentum transfer in Ni-Al collision sequences along 〈1 1 1〉 lattice directions. The low efficiency of momentum transfer due to the mass mismatch can also be responsible for the experimental observation that the preferential ejections in the alloy were less prominent than those in the Ni metal.     

Observation of the 1S0-->3P0 clock transition in 27Al+

We report, for the first time, laser spectroscopy of the 1S0-->3P0 clock transition in 27Al+. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminum's electronic state to the beryllium's hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency nu=1,121,015,393,207,851(6) Hz. They are also used to measure the lifetime of the metastable clock state tau=20.6+/-1.4 s, the ground state 1S0 g factor gS=-0.000,792,48(14), and the excited state 3P0 g factor gP=-0.001,976,86(21), in units of the Bohr magneton.     

Effect of the spiral phase element on the radial-polarization (0, 1) LG beam

Radially-polarized beams can be strongly amplified without significant birefringent-induced aberrations. However, radially-polarized beam is a high-order beam, and therefore has to be transformed into a fundamental Gaussian beam for reduction the beam-propagation factor M². In effort to transform the radially-polarized beam to a nearly-Gaussian beam, we consider effect of a spiral phase element (SPE) on the Laguerre-Gaussian (LG) (0, 1)^∗ beam with radial polarization, and compare this with the case when the input beam is a LG (0, 1)^∗ beam with spiral phase and uniform or random polarization. The LG (0, 1)^∗ beam with radial polarization, despite its identity in intensity profile to the beam with spiral phase, has distinctly different properties when interacting with the SPE. With the SPE and spatial filter, we transformed the radially-polarized (0, 1)^∗ mode with M² = 2.8 to a nearly-Gaussian beam with M² = 1.7. Measured transformation efficiency was 50%, and the beam brightness P/(M²)² was practically unchanged. The SPE affects polarization state of the radially-polarized beam, leading to appearance of spin angular momentum in the beam center at the far-field.     

Experimental determination of the helium 2(3)P(1)-1(1)S0 transition rate

We present the first experimental determination of the 2(3)P(1)-1(1)S0 transition rate in helium and compare this measurement with theoretical quantum-electrodynamic predictions. The experiment exploits the very long (approximately 1 minute) confinement times obtained for atoms magneto-optically trapped in an apparatus used to create a Bose-Einstein condensate of metastable (2(3)S1) helium. The 2(3)P(1)-1(1)S0 transition rate is measured directly from the decay rate of the cold atomic cloud following 1083 nm laser excitation from the 2(3)S1 to the 2(3)P1 state, and from accurate knowledge of the 2(3)P1 population. The value obtained is 177+/-8 s(-1), which agrees very well with theoretical predictions, and has an accuracy that compares favorably with measurements for the same transition in heliumlike ions higher in the isoelectronic sequence.     

Effect of residual oxygen on ionization processes of Si and Si sputtered from Si(1 1 1)-7 × 7 surface

The effect of residual oxygen impurity on ionization processes of Si⁺ and Si²⁺ has been studied quantitatively. In this study, ion sputtering experiments were carried out for a Si(1 1 1)-7 × 7 surface, irradiated with 9-11 keV Ar⁰ and Kr⁰ beam. Even if the oxygen concentration is less than the detection limit of Auger electron spectrometry, SiO⁺ and SiO₂⁺ ions have been appreciably observed. Moreover, as the SiO⁺ and SiO₂⁺ yields increases, the Si⁺ yield is slightly enhanced, whereas the Si²⁺ yield is significantly reduced. From the incidence angle dependence of secondary ion yields, it is confirmed that Si⁺* (Si⁺ with a 2p hole) created in the shallow region from the surface exclusively contributes to Si²⁺ formation. By assuming that the SiO⁺ and SiO₂⁺ yields are proportional to the residual oxygen concentration, these observations are reasonably explained: The increase of Si⁺ with the increase of residual oxygen is caused by a similar effect commonly observed for oxidized surfaces. The decrease of Si²⁺ yield can be explained by the inter-atomic Auger transition between the residual oxygen impurity and Si⁺*, which efficiently interferes the Si²⁺ formation process.     

Improved measurement of the 1s2s 1S0-1s2p 3P1 interval in heliumlike silicon

Using colinear fast-beam laser spectroscopy with copropagating and counter-propagating beams we have measured the 1s2s 1S0-1s2p 3P1 intercombination interval in 28Si12+ with the result 7230.585(6) cm{-1}. The experiment made use of a dual-wavelength, high-finesse, power build-up cavity excited by single-frequency lasers at 1319 and 1450 nm. The result will provide a precision test of ab initio relativistic many-body atomic theory at moderate Z.     

Ultrathin Fe films on single crystal and virtual Ge(0 0 1) substrates: Towards the control of magnetic properties

Ultrathin Fe films have been epitaxially grown at room temperature on standard single crystal Ge(0 0 1) substrates and virtual Ge/Si(0 0 1) substrates. Their magnetic and electronic properties have been investigated in situ by spin polarized inverse photoemission and magneto-optical Kerr effect. In both cases, the onset of ferromagnetism appears definitively at 3 ML, and the overall behavior is very similar in the case of standard and virtual substrates, so that the latter can be employed for growing high quality Fe/Ge/Si interfaces. All the films investigated display uniaxial anisotropy, which is explained in terms of the surface morphology induced by the preparation conditions.     

Effects of thermal treatment on the morphology of Alq3 thin layers on Si(1 1 1) substrate

Alq₃ thin layers were vapor deposited onto a single crystal of Si(1 1 1) and the morphology of the surface was investigated by the scanning tunneling microscope under ultrahigh vacuum conditions. The STM imaging showed considerable influence of the thermal processing onto the topography of the sample. Slowly raising the sample temperature to ∼160 °C caused a complete desorption of Alq₃ molecules and uncovering the clean surface of Si(1 1 1). A fast rise of the temperature (flashing) to ∼600 °C led to decomposition of the Alq₃ and resulted in remnants of a carbon-rich surface species. Then heating or flashing this surface to a temperature in excess of 1000 °C brought about the occurrence of regular shape object on the Si(1 1 1) surface.     

CW ultraviolet saturation spectroscopy of the 6p 3P0-9s 3S1 transition in mercury at 246.5 nm

We have measured the even isotope structure of the 6p ³P₀-9s ³S₁ transition in mercury at 246.5 nm using saturated absorption spectroscopy with radiation produced as the sum frequency of a 363.8 nm argon ion laser and an LD700 ring dye laser in ADP. This is the first use of cw sum-frequency mixing in nonlinear laser spectroscopy in the ultraviolet. No previous cw Doppler-free measurements have been reported at wavelenghts below 294.5 nm