A new and unusual phenomenon which we call light narrowing is reported and discussed in this paper. We discovered this effect in dense, spin-polarized cesium vapor optically pumped with a cw blue dye laser beam tuned to the second resonance ${D}_{1}$ line (4593 \AA{}). We observe a significant narrowing of the radio-frequency power-broadened magnetic resonance lines (linewidths narrow by as much as a factor of 2.5) when the intensity of the circularly polarized incident dye laser beam is increased by either focusing the beam or by the removal of attenuating filters from the focused beam. The magnetic resonance linewidths in spin-polarized cesium vapor were measured over a wide range of cesium number densities (5\ifmmode\times\else\texttimes\fi{}${10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ \ensuremath{\le}[Cs]\ensuremath{\le}1\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\ensuremath{-}3}$). This corresponds to cesium spinexchange rates of 4.5\ifmmode\times\else\texttimes\fi{}${10}^{3}$ to 9\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ${\mathrm{sec}}^{\ensuremath{-}1}$. For low cesium number densities (5\ifmmode\times\else\texttimes\fi{}${10}^{12}$ [Cs]3\ifmmode\times\else\texttimes\fi{}${10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) the light-narrowing effect is large (a factor of 2.5) and independent of [Cs]. In the region of 3\ifmmode\times\else\texttimes\fi{}${10}^{14}$ to 1\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ in number densities, the light-narrowing effect decreases with increasing [Cs]. At high cesium number densities ([Cs]> 1\ifmmode\times\else\texttimes\fi{}${10}^{15}$ ${\mathrm{cm}}^{\ensuremath{-}3}$) this light-narrowing effect almost completely disappears. In the limit of low-radio-frequency power the magnetic resonance linewidths for focused and unfocused dye laser beam are nearly the same. Experimental observations on this new effect are presented in detail. In the latter part of this paper a self-contained theoretical treatment of the light-narrowing effect is developed. Using Bloch equations in the presence of optical pumping, spin relaxation (diffusion, electron randomization), rapid spin exchange, and radio-frequency magnetic field, expressions for magnetic resonance line shapes are derived. In general, we find good agreement between our experimental results and the theory.
Continuous-wave lasing in optically pumped atomic cesium and rubidium vapor is observed without the use of any feedback mirrors. The stimulated emission in a number of infrared wavelengths is restricted to a very narrow angle in both the forward and backward directions.
Relative mass abundances of singly charged cesium-cluster ions (${\mathrm{Cs}}_{\mathit{n}}^{+}$) extracted from a liquid-metal ion source show sharp decremental steps at n=3, 5, 9, and 21 and a pronounced minimum at ${\mathrm{Cs}}_{10}^{+}$. In the region of n>9, ${\mathrm{Cs}}_{13}^{+}$ shows a maximum in the relative abundance. The time-of-flight technique is used to obtain the mass spectrum. The prominent features observed at n=9 and 21 are interpreted using the shell structure of simple metal clusters. ${\mathrm{Cs}}_{9}^{+}$ and ${\mathrm{Cs}}_{21}^{+}$, which contain 8 and 20 valence electrons, respectively, form closed-shell configurations with enhanced relative stabilities.
We have used spectrally broadened counterpropagating radiation from tunable diode lasers to cool an atomic beam of cesium. This produces a continuous beam of cold atoms. The injection current to the single-mode diode laser is modulated at 10 MHz, resulting in spectrally broadened light for atomic cooling and optical pumping. The atomic beam is probed with a weak single-mode laser. This is a simple and relatively inexpensive method for producing a continuous supply of cold atoms.
A new method for measuring cross sections for the scattering of electrons by laser-excited atoms is described. It is a generalization of the atomic-beam recoil technique, taking advantage of the recoil of atoms during resonant photon interactions to spatially separate excited from nonexcited atoms. A preliminary value for the total cross section for the scattering of electrons by the $3^{2}P_{\frac{3}{2}}({m}_{F}=3)$ state of sodium at 4.4 eV is presented.
We have seen a new region of absorption in saturated sodium vapor in the infrared region of the spectrum (0.83–2.5 μ). The absorption from 0.83 to 1.18 μ may be the analog of the ultraviolet emission continuum of H2, possibly arising from the sodium dimer (3Σu+→3Σg+) transition, along with contributions from higher sodium polymers. Absorption at longer wavelength is most likely due to higher polymers of sodium (Na3, Na4,...).
Results of experimental investigations of the cesium (Cs) gettering properties of graphite at various temperatures are reported. Possible reasons for this behavior are discussed. A model based on the grain boundary and surface diffusion of Cs in graphite is used to explain the results. Using this model, the activation energy for surface/grain boundary diffusion of Cs into polycrystalline graphite is estimated to be ~14 kcal/mole. The initial motivation was to examine the performance of graphite getters used in the cesium beam tube frequency standards. New results are presented regarding the dramatic improvement in the Cs gettering efficiency of graphite when heated to and maintained at elevated temperatures (100-130 degrees C) over the room-temperature efficiency.
Currently liquid metal ion sources (LMISs) are of great interest for a wide variety of applications—ion implantation, ion microlithography, thrusters for electric space propulsion, etc. A novel application of the LMIS is for the production of metallic cluster ions. In our laboratory we have designed and optimized the performance of a LMIS for the production of cluster ions of alkali metals. Using liquid rubidium (Rb) we have observed copious production of singly charged cluster ions (Rb+N, N=1–100). As expected the largest fraction of the emission consists of atomic ions. For low source current (<5 μA) about 80% of the total emission current is that of Rb+. The remaining 20% consists of Rb+2 and Rb+3. However, for large emission currents (>80 μA) we observe cluster ions as large as Rb+100. We study the mass distribution using the time-of-flight technique.
Cs gettering properties are investigated for colloidal graphites containing graphite particles suspended in various types of solvents (termed 'primary vehicle') and binders. The gettering performance is studied by measuring the Cs sticking coefficient on stainless steel surfaces coated with colloidal graphite. The colloids Electrodag 121, Electrodag 179 and Aquadag E are used. They all contain water as the primary vehicle with different binders (organic and inorganic). Out of the three, only Aquadag E shows any significant Cs gettering capability. The other two behave essentially like uncoated metal surfaces. The results together with possible reasons for this behavior are presented.< >
