Showing papers on "Stark effect published in 1981"

Accurate calculation of dynamic Stark shifts and depopulation rates of Rydberg energy levels induced by blackbody radiation. Hydrogen, helium, and alkali-metal atoms

Abstract: A highly excited (Rydberg) atom bathed in blackbody radiation is perturbed in two ways. A dynamic Stark shift is induced by the off-resonant components of the blackbody radiation. Additionally, electric-dipole transitions to other atomic energy levels are induced by the resonant components of the blackbody radiation. This depopulation effect shortens the Rydberg-state lifetime, thereby broadening the energy level. Calculations of these two effects in many states of hydrogen, helium, and the alkali-metal atoms Li, Na, K, Rb, and Cs are presented for $T=300$ K. Contributions from the entire blackbody spectrum and from both discrete and continuous perturbing states are included. The accuracy is considerably greater than that of previous estimates.

Free ion and crystal field parameters for REOCl : Eu3+

Abstract: The fluorescence spectra of Eu3+ activated rare earth oxychlorides REOCl : Eu3+ (RE = Y, La, Gd) were recorded and analyzed at 4.2, 77, and 300 K. For each compound more than 100 transitions between the Stark levels of the 4f6 configuration were observed and assigned. The energy level schemes established from the spectra show a relatively strong crystal field effect. The five nonzero crystal field parameters for the C4v point site symmetry occupied by the rare earth ion were determined, yielding a mean square deviation of a few cm−1. The free‐ion parameters were also determined with the aid of excitation spectra. The effect of truncation of the basis set of the 2S+1LJ levels on the energy level simulation of the excited levels was also studied.

Absorption of additional photons in the multiphoton ionisation continuum of xenon at 1064, 532 and 440 nm

Abstract: The energy spectrum of electrons produced by multiphoton ionisation of xenon atoms has been measured, using a new type of electron energy analyser with an acceptance angle of 2 pi sr. Absorption of additional photons above the minimum number required for ionisation has been observed in the non-resonant as well as in the resonant multiphoton ionisation process. In the resonant proces the AC Stark shift is used to link wavelength detuning to the light intensity, in order to find the probability of extra photon absorption as a function of light intensity.

Stark broadening of visible neutral helium lines in a plasma.

Abstract: Side-on observations of the visible spectrum emitted by a helium plasma generated in a wall-stabilized arc are reported. Electron densities range from 0.2 to 1.3 × 10 22 m -3 and electron temperatures vary from 10,000 to 20,000 K. Most of the seventeen measured lines are “isolated” at the conditions of the experiment. Here, “isolated” refers to quantum levels which are non-degenerate even in the presence of perturbing fields. Electron densities derived from the Stark-widths of the isolated lines agree to within 15% of the values determined from Hβ and from the quasi-degenerate He(I) lines at 4471 and 4921 A. Similar agreement is observed for the static-ion Stark broadening parameters. However, at the conditions of this experiment, the static-ion approximation is not valid near the center of some of the isolated lines. The observation of ion-dynamic effects in neutral isolated lines is reported here for the first time. In the isolated lines, the measured ion-dynamic effects are reasonably consistent with calculations based on an adiabatic “unified” theory for the ion perturbers. A simple parametric expression closely approximates the ion-dynamic contribution to the half-width of isolated lines. Hydrogenic (non-isolated) neutral helium lines exhibit a large discrepancy with theoretical profiles near the line center, where ion-dynamic effects are important.

Observation of Surface States on Ag(100) by Infrared and Visible Electroreflectance Spectroscopy

Abstract: By use of the new technique of electroreflectance in the infrared frequency range, a low-lying unoccupied surface state on the (100) single-crystal surface of Ag was detected. Another absorption feature, due to excitation into a higher surface state, has been seen around 3.1 eV. The positions of the two surface states are in good agreement with the calculated values. A study of the Stark shift of these states has revealed that the electric field near the metal surface has a much more complex structure than hitherto recognized.

Stark Acceleration of Rydberg Atoms in Inhomogeneous Electric Fields

Abstract: A method is proposed to decelerate neutral atoms in a thermal beam for purposes of precision spectroscopy, atomic clocks, or loading into shallow traps. Rydberg atoms exhibit large electric dipole moments suggesting that inhomogenous fields can exert forces on them. The resultant change in kinetic energy is equal to the Stark shift of the Rydberg state. It has been found that a series of tandem electrode pairs can reduce atomic velocities by a factor of 10. Various limitations and constraints are discussed.

Investigation of the Stark broadening of Balmer beta

Abstract: The Stark broadening of the Balmer line Hbeta was studied in a high-current wall-stabilised arc at electron densities between 1.75 and 14.4*1016 cm-3. The electron density was obtained by means of a two-wavelength Michelson interferometer. The reduced half-widths of Hbeta were compared with the theories of Griem et al. (1962), Vidal et al. (1973) and Seidel (1977). A slight increase in the reduced half-widths with increasing electron density was observed, just as predicted by theory. The absolute values, however, were smaller than the theoretical ones. There was good agreement with the experimental data of Bassler and Kock. The results of Wiese, Kelleher and Paquette (1972) differ from the data by 5-10% depending on the electron density.

Mono-Ion Oscillator as Potential Ultimate Laser Frequency Standard

Abstract: An individual atomic ion localized in the center of a small Paul rf quadrupole trap has potential as an ultimate laser frequency standard because, broadly speaking, the ion may be brought to "A State of Complete Rest in Free Space" by side band cooling. As a consequence, all Doppler shifts vanish. "Free Space" is approximated insofar as the electric trapping field vanishes in the center of the trap and there is no Stark effect. Neither need there be a Zeeman Effect as magnetic fields may be controlled down to the micro-Gauss range. Naturally, there is no transit time broadening. Minute laser powers provided by harmonic generators suffice for saturation of optical transitions as well focused beams may be used. Millionfold atomic amplification of the single-ion fluorescence from a metastable level may bring resolutions of 1 part in 10" within reach.

Avoided‐crossing molecular‐beam experiments on fluoroform (CF3H) and fluoroform‐d (CF3D)

Abstract: The avoided‐crossing molecular‐beam method for studying normally forbidden (ΔK≠O) transitions in symmetric tops has been applied to fluoroform (CF3H) and fluoroform‐d (CF3D), thus marking the extension of the method to systems which are not near spherical rotors. In order to reach the high electric fields required while still retaining the necessarily narrow linewidth, the electric resonance spectrometer has been equipped with a new pair of Stark plates capable of providing electric fields up to about 20 kV/cm with a homogeneity of 1 part in 105 over a length of 3 cm. The anticrossing (J,K) = (1,0)↔(1,±1) has been studied for both CF3H and CF3D. In each case, the rotational constant C0 along the symmetry axis has been obtained to 0.002%. From anticrossing spectra observed in combined electric and magnetic fields, the signs of the rotational g factors g∥ and g⊥ have been shown to be negative. From a conventional molecular beam study for each isotopic species, a value of the permanent electric dipole moment...

ac Stark splitting in intense stochastic driving fields with Gaussian statistics and non-Lorentzian line shape

Abstract: Lorentzian models for laser line shapes lead to qualitatively incorrect results for off-resonance excitation of atoms. This paper is the first attempt to present a theory of the nonperturbative interaction of an atom with a chaotic field (representing multimode laser radiation having strong amplitude fluctuations) with a line shape falling off faster than a Lorentzian. To this end we suggest a stochastic Markovian model for a non-Lorentzian chaotic field. To solve the multiplicative stochastic differential equations describing the atom-field interaction we propose a "marginal characteristic function approach." This not only reproduces our earlier results in a more elegant way and establishes the relationship between approaches used by other authors in a different context, but also provides the simplest possible basis for our present discussion of ac Stark splitting in double optical resonance. While for a chaotic field with a Lorentzian line shape the asymmetry of the two-peaked off-resonance spectrum is reversed for all values of the detuning compared with the monochromatic case, our present model predicts a reversed peak asymmetry only for detunings smaller than a few laser bandwidths in agreement with experiment. The on-resonance spectrum is dominated by the amplitude fluctuations and is only weakly affected by changes of the spectral line shape of the laser.

Adiabatic theorem and spectral concentration. I. Arbitrary order spectral concentration for the Stark effect in atomic physics

Abstract: The spectral concentration of arbitrary order for the Stark effect is proved to exist for a large class of Hamiltonians appearing in nonrelativistic and relativistic quantum mechanics. The results are consequences of an abstract result about the spectral concentration for self-adjoint operators. A general form of the adiabatic theorem of quantum mechanics, generalizing an earlier result of the author as well as some results by Lenard, is also proved.

Stark effect of nonhydrogenic Rydberg spectra

Abstract: Rydberg states of an atom in an electric field are represented in terms of hydrogen eigenfunctions for the same field but scattered by the ionic core of the actual atom. The effect of the Stark field on photoabsorption is expressed in terms of scattering and frame-transformation parameters.

Sub-Doppler resolution infrared molecular-beam spectroscopy. Stark effect measurement of the dipole moment of hydrogen fluoride and hydrogen cyanide in excited vibrational states

Abstract: Sub-Doppler beam-calorimetric infrared spectroscopy is used to determine the dipole moments of hydrogen fluoride and hydrogen cyanide in vibrationally excited states. For the former µ1= 1.872 ± 0.003 D while for the latter µ001= 3.012 ± 0.002 D. The results for hydrogen fluoride are used to revise the literature value of µe for this molecule to 1.803 ± 0.002 D.

Highly excited atoms

Abstract: Highly excited atoms are often called Rydberg atoms. These atoms have a wealth of exotic properties which are discussed. Of special interest, are the effects of electric and magnetic fields on Rydberg atoms. Ordinary atoms are scarcely affected by an applied electric or magnetic field; Rydberg atoms can be strongly distorted and even pulled apart by a relatively weak electric field, and they can be squeezed into unexpected shapes by a magnetic field. Studies of the structure of Rydberg atoms in electric and magnetic fields have revealed dramatic atomic phenomena that had not been observed before. (SC)

Multiresonant behavior in nearly degenerate four-wave mixing: the ac Stark effect.

Abstract: We have experimentally studied the effects of pump–probe detuning in nearly degenerate four-wave mixing. The data show multiresonant behavior as a function of the pump–probe detuning at both low and high intensities. At low intensities, the structure is the result of Doppler motion. At high intensities, five-peak structure is observed and is explained by the standing-wave modulation of the ac Stark splitting of the atomic levels.

Electron Number Densities in Analytical Inductively Coupled Plasmas as Determined via Series Limit Line Merging

Abstract: A convenient and a rapid technique is introduced to estimate the electron number densities, ne, in inductively coupled plasmas. The method is based on previously reported observations that the principal quantum number of the last discernible line in a series limit depends on ne. The spatially integrated ne values, as determined from the spectra of H, Li, Mg, Al, Ca, and K emitted in a pure Ar plasma ranged between ∼4 × 1014 and ∼3 × 1015 cm−3 for various forward powers and observation heights. These results agreed with ne values derived from other methodologies such as the Stark broadening and absolute continuum intensity.

Resonances in the Stark Effect of Atomic Systems

Abstract: Generalizing earlier results on the Hydrogen case it is proved, through a dilation analyticity technique different from the canonical one, that the action of a weak electric field shifts the isolated eigenvalues of any atomic system into resonances of the Stark effect, uniquely determined by the perturbation series through the Borel summation method.

Electric dipole moment of KrSO3

Abstract: The radiofrequency spectrum of KrSO3 is reported A beam of KrSO3 was produced by expanding a mixture of Ar, Kr and SO3 at 900 Torr through a nozzle at 25°C The Stark spectrum and dipole moment are reported

Possibility of experimental separation of resonances and cusps from background in electron scattering

Abstract: It is shown, with the help of model calculations, that a laser field can be used to suppress the background in electron scattering cross sections and to pick out only those parts which are rapidly varying as functions of the incoming electron energy. Therefore it becomes possible to measure the pure Breit-Wigner peaks and threshold effects, independent of the fact that interference between the resonances and the background in radiationless electron scattering is strong. The results are interpreted within the low-frequency limit for free-free transitions. The ac Stark shift of the resonance is also observed.

Precise measurement of the static electric field ionization rate for resolved hydrogen Stark substates

Abstract: We report the first precise measurements of the ionization rate ${\ensuremath{\Gamma}}_{I}(F)$ in the tunneling regime for resolved $n=30,40$ Stark substates of hydrogen. Excellent agreement is obtained with nonrelativistic numerical calculations. No effects of wave function mixing induced by relativistic or other interactions were observed. We consider and give an experimental upper limit for the magnitude of the H-D isotopic shift in ${\ensuremath{\Gamma}}_{I}(F)$.