Cesium Atomic Beam Research Articles

Precision lifetime measurements of the 6p2P1/2,3/2 states in atomic cesium.

We report measurements of the 6${\mathit{p}}^{2}$${\mathit{P}}_{1/2}$ and 6${\mathit{p}}^{2}$${\mathit{P}}_{3/2}$ state lifetimes in the $^{133}\mathrm{Cs}$ atom with precisions of 0.23% and 0.27%, respectively. The results are important to the interpretation of the next generation of parity nonconservation experiments in atomic cesium. A diode laser was used to selectively excite a fast beam of neutral cesium atoms. The decay in flight of the fluorescence was observed with photon-counting detectors. The lifetime results are 34.934\ifmmode\pm\else\textpm\fi{}0.094 ns for the 6${\mathit{p}}^{2}$${\mathit{P}}_{1/2}$ state and 30.499\ifmmode\pm\else\textpm\fi{}0.070 ns for the 6${\mathit{p}}^{2}$${\mathit{P}}_{3/2}$ state. We present comparisons with previous measurements and with relativistic many-body calculations of alkali-metal-atom transition matrix elements.

Angular Distribution Measurement of Cesium Atomic Beam from Long Tube Collimators

Angular distribution of a cesium atomic beam effusing from long tube collimators with circular cross section was measured. Two types of collimators, a stainless steel tube ( 0.7 mmφ×20 mm) and a glass capillary array ( 50 µmφ×2 mm) were examined. The glass capillary array was superior in terms of collimation and Cs consumption, and this was attributed to its small dimension.

Optical spin polarization and state-sensitive detection of a cesium atomic beam.

A cesium atomic beam having a high degree of polarization is prepared by optical pumping with two circularly polarized diode lasers, and a technique for state-sensitive atomic detection involving laser-induced fluorescence in a magnetic field (LIFB) is introduced. An atomic-beam polarization of 93% is measured using the LIFB technique, and the combined use of optical-state preparation and LIFB detection in an atomic-recoil experiment to study spin-changing electron-atom collisions is demonstrated.

Semiconductor laser excitation of Ramsey fringes by using a Raman transition in a cesium atomic beam

An amplitude-modulated semiconductor laser is used to excite a 9.2-GHz Raman transition in a cesium atomic beam. Separated-field Ramsey fringes as narrow as 1 kHz wide are observed with a high signal-to-noise ratio, even for semiconductor laser linewidths as wide as 20 MHz. These narrow resonances have potential application in the development of high-accuracy, optically excited atomic clocks.

Multistability in the laser cooling of atomic beams

We describe the interaction of a beam of two-level atoms with multiple laser beams propagating in the opposite direction. The lasers are frequency-chirped in order to remain close to resonance and they continuously decelerate the atoms by radiation pressure. In a deterministic treatment, the average atomic velocity exhibits multistability cycles as a function of the chirping rate. A statistical (Fokker-Planck) treatment shows the corresponding splitting of the atomic velocity distribution into well-separate, quasi-monokinetic bunches of atoms. In the laboratory reference frame, multistability shows up through the increasingly decelerated motion of these atomic bunches. Analytical results are presented, as well as numerical simulations for a beam of cesium atoms, both in the laboratory frame and in the non-inertial frame. The conditions for the observation of multiple cooling with frequency-chirped lasers are discussed. A comparison with standard chirped cooling is outlined. Possible applications are indicated.

High-brightness, high-purity spin-polarized cesium beam.

We describe a cesium atomic beam (${10}^{14}$ atoms ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$, 6\ifmmode\times\else\texttimes\fi{}${10}^{16}$ atoms ${\mathrm{sr}}^{\mathrm{\ensuremath{-}}1}$ ${\mathrm{s}}^{\mathrm{\ensuremath{-}}1}$) spin polarized using light from two diode lasers. Of the atoms, 95% may be placed into either the 6${\mathit{S}}_{1/2}$(F,${\mathit{m}}_{\mathit{F}}$)=(3,3) or (4,4) state, with less than 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ of the atoms left in the depleted hyperfine level. The latter fraction rises linearly with atomic beam intensity because of reabsorption of light scattered during the optical pumping process. This and other effects limiting complete hyperfine pumping are discussed.

Spin-exchange frequency shift in a cesium atomic fountain.

In connection with experiments aiming at the improvement of the cesium atomic beam clock by means of a fountain of laser-cooled cesium atoms, we present expressions for the line shift and line broadening due to collisions between cesium atoms. The coherent collision cross sections occurring in these expressions are calculated by means of the coupled-channels method. The magnitude of the calculated shift implies that spin-exchange collisions are an important factor in limiting the anticipated accuracy of a future cesium fountain clock and of other intended fountain experiments.

Microwave resonance on a laser-cooled cesium beam: prospects for a cesium frequency standard

The atomic clock transition ( F=3, M F =0↔F=4, M F =0) has been studied on a laser-cooled cesium atomic beam. Diode lasers have been used for laser cooling of the atoms, and for preparation and detection of the microwave transition. Both Rabi spectra and Ramsey fringes have been obtained. The observed lineshapes are characteristic of the narrow velocity distribution of the atoms. The residual width of the velocity distribution was estimated from the observation of Rabi oscillations. The high signal-to-noise ratio of the experimental spectra demonstrate the attractive possibilities opened by laser cooling in spectroscopy and frequency standard applications.

Optical pumping with two finite linewidth lasers.

Two-laser optical pumping schemes show great promise for atom preparation since they can act as a nearly perfect state selector. This paper presents a new theoretical model to evaluate the pumping efficiency of two-laser pumping schemes, taking into account optical, ground and excited states hyperfine and Zeeman coherences, neighboring transitions, and fluctuating laser fields. The model is used to predict the optical pumping efficiency of two lasers with Lorentzian spectral profiles on a beam of cesium atoms. The particular laser intensities and linewidths that optimize the optical pumping efficiency and rate are calculated.

Formation of a narrow velocity distribution in an atomic cesium beam by resonant injection laser radiation

An experimental investigation was made of a steady-state deceleration of a beam of cesium atoms by resonant radiation from an injection laser with an external resonator characterized by an emission line of width (Γ < 1 MHz) less than the natural width of the D2 line. A steady-state narrow peak of the velocity distribution was ~ 13 m/s wide, corresponding to an effective temperature of ~ 1 K.

Atomic beam collimation using a laser diode with a self-locking power-buildup cavity

We have demonstrated a self-locking power-buildup cavity for laser diodes. This device requires only a few simple optical elements and can provide a standing wave containing as much as 1000 times the power emitted by the laser diode. With this device we have obtained an intense standing wave of tunable light that was used to collimate a cesium atomic beam. We have studied the power and frequency dependence of the beam collimation.

Cooling atoms with stimulated emission.

We have observed an efficient collimation of a cesium atomic beam crossing at right angles an intense laser standing wave. This new cooling scheme is mainly based on a redistribution of photons between the two counterpropagating waves by the moving atoms. By contrast with usual radiation pressure cooling, this stimulated molasses works for blue detuning and does not saturate at high intensity.

Manipulating atomic velocities using diode lasers

We have used counterpropagating radiation from a diode laser to cool and stop a beam of cesium atoms. The laser frequency was chirped to keep it in resonance with the slowing atoms. The same laser was used to probe the resulting velocity distributions. We have cooled more than 1010 atoms/sec to a temperature of 1 K. This is an extremely simple and inexpensive way to manipulate atomic velocities and has a wide range of possible applications.

Recent Investigations into the Shape of the Ramsey Resonance Pattern in a Cesium Atomic Clock

The influence of the velocity distribution on the shape of the Ramsey resonance pattern has been investigated both theoretically and experimentally using CSX, the PTB's experimental cesium atomic beam device. It is shown that a distortion (gaps) in the velocity distribution of the beam atoms may lead to the modulations on the Rabi pedestals which were recently observed in the NRLM-II frequency standard in Japan.

Steady‐state clock phase behavoir in loosely coupled master‐slave synchronization network

AbstractIn the Japanese master‐slave synchronization network, the introduction of the cesium atomic beam frequency standard as the master office oscillator for improving the frequency accuracy, and the introduction of a loosely coupled synchronization network using the digital processing type phase‐locked oscillator to improve the clock reliability, are scheduled. An analysis is made of the clock phase behavior of a multi‐link digital clock supply in the steady state. The influence on the clock phase variation by transmission line jitter and DCS (digital clock supply) temperature dependence is considered. The results are expressed by two‐sample variance ßy2(±) which shows short‐term frequency stability, and then by time interval error (TIE) which shows phase fluctuation in the time domain. The results obtained from numerical calculation give maximum TIE of the distributed clock in the domestic 9‐linked DCS (about 25 μs) and a permissible synchronization network within three links for international digital connections by comparison with the TIE recommended by CCITT.

Hyperfine-structure measurement of the7Sstate of cesium

The hyperfine structure of the $7{S}_{\frac{1}{2}}$ state of $^{133}\mathrm{Cs}$ has been measured with the use of laser spectroscopy on a cesium atomic beam. We find the magnetic dipole coupling constant $A=545.90(09)$ MHz. From the amplitude of the hyperfine components we find the ratio of the scalar to tensor polarizabilities ($|\frac{\ensuremath{\alpha}}{\ensuremath{\beta}}|$) for the $6S\ensuremath{\rightarrow}7S$ transition to be 9.80(12).

Spatial Profiles of a Deflected Cesium Atomic Beam

Spatial Profiles of a Deflected Cesium Atomic Beam

Absolute determination of two- and four-photon ionisation cross sections of caesium atoms

The radiation of a linearly polarised single-mode Q switched laser is made to interact with a caesium atomic beam. The laser wavelengths (528 nm and 1056 nm) are chosen so that the authors deal unambiguously with non-resonant processes. Two kinds of laser focusing are used, leading to identical results within the error bars. This procedure takes account of intensity distribution and interaction volume effects. The cross section values are sigma 2=(6.7+or-1.9)*10-50 cm4 s for two-photon ionisation and sigma 4=(7.5+or-2.8)*10-109 cm8 s3 for four-photon ionisation.

Production of PolarizedH−orD−Ions by a Colliding-Beam Method

An experiment is described which shows that a 3-\ensuremath{\mu}A beam of polarized ${\mathrm{H}}^{\ensuremath{-}}$ of ${\mathrm{D}}^{\ensuremath{-}}$ ions can be produced by bombarding polarized thermal hydrogen atoms with a beam of 40-keV cesium atoms. The observed beam polarization is consistent with the assumption that there is no depolarization in the collision ${({\mathrm{H}}^{0})}_{\mathrm{pol}}$ + ${\mathrm{Cs}}^{0}$ \ensuremath{\rightarrow} ${({\mathrm{H}}^{\ensuremath{-}})}_{\mathrm{pol}}$ + ${\mathrm{Cs}}^{+}$. The emittance of the beam is sufficiently small for good transmission through tandem accelerators.

Spin Dependent Charge Transfer in Low-Energy Collisions between Helium Ions and Cesium Atoms

The experiment demonstrated that total spin angular momentum is conserved in the near resonant charge transfer collisions between oriented helium ions and oriented cesium atoms. The resulting spin dependence of the total charge transfer cross-sections is described using singlet and triplet channels based on the molecular potential energy curves of the collision pair. The experiment was performed with helium ions stored in a rf-quadrupole trap in interaction with an optically pumped beam of cesium atoms. Total spin dependent charge transfer cross-sections were measured in the energy range of a few eV.