C Delsart

Pulsed photodetachment microscopy and the electron affinity of iodine

Photodetachment microscopy is carried out on a beam of 127I− ions with a nanosecond pulsed laser. The photoelectron interferograms are recorded by means of a digital camera that images the light spots produced by the amplified photoelectrons on a phosphor screen. This is the first implementation of such an optical imaging technique in photodetachment microscopy. Due to their sensitivity to the photoelectron energy, the recorded electron interferograms can be quantitatively analysed to produce a measure of the electron affinity of iodine eA(127I) with an accuracy improved by more than a factor of 2 with respect to the best previous measurement. The result is 2467 287.4(29) m−1 or 3.059 0463(38) eV.

The fine structure of S and S − measured with the photodetachment microscope

Photodetachment microscopy of a beam of 32S− ions makes it possible to measure the detachment thresholds corresponding to different fine-structure levels of the negative ion S− and the neutral atom S. The electron affinity of sulfur, at 2.077 eV, is well suited for detachment by a tunable dye laser, which provides a third way of measuring neutral S fine structure, besides VUV spectroscopy of S I lines and direct fine-structure resonance spectroscopy. The fine-structure intervals are found to be 48 353.52(34) m−1 for the 2P1/2 − 2P3/2 energy difference in S−, and 39 605.87(32) m−1 for the 3P1 − 3P2 one in S (with expanded uncertainties), consistent with an independent measurement of the 3P0 − 3P1 interval. The new recommended electron affinity for isotope 32 of sulfur is 1675 297.60(42) m−1, or 2.077 104 18(71) eV.

Observation of the optical Autler-Townes splitting in neon gas with a cascade level scheme

The optical Autler-Townes effect (dynamic Stark splitting) induced by a single-mode CW dye laser has been observed in neon gas with a cascade level scheme and a He-Ne probe beam. The splitting is found to be proportional to the square root of the saturating laser power and independent of the detuning. The existence of two Rabi nutation frequencies due to level degeneracy is clearly shown by changing the polarization axis of the probe beam.

Measurement of the three-photon detachment cross sections of the negative ions of iodine, bromine and fluorine at the wavelength 1.0642 mu m

The three-photon detachment cross sections of the ions F-, Br- and I- are measured, using the fundamental 1064.2 nm wavelength of a single-mode Nd:YAG laser. The detachment signal is measured by detecting the neutral atoms produced from an ionic beam of kinetic energy 1.2 keV. The data analysis takes into account the laser pulse time profile, the actual spatial profile of the laser beam in the interaction region, and the fast motion of the ions through the laser beam during the laser pulse. Saturation of the three-photon process is observed and used to normalise the detachment signal. The authors obtain sigma (F-)=6.1

Photodetachment microscopy to an excited spectral term and the electron affinity of phosphorus

+2.6-1.8*10-95 s2 m6, sigma (Br-)=1.6+0.8-0.6*10-94 m6 and sigma (I-)=3.3+16-1.1*10-94 s2 m6. These measured cross sections are compared with theoretical predictions. The result obtained on F- agrees with a very recent measurement performed with a different technique.

Photodetachment microscopy of O

A beam of P− ions produced by a cesium sputtering ion source was photodetached in the presence of an electric field, with a single-mode ring dye laser. Neutral P can be produced at one or the other of the fine-structure sub-levels of its 3s23p3 2Do excited term. This is the first atomic photodetachment microscopy experiment with excitation of the parent neutral atom out of the fundamental spectral term. The background electron signal due to ground-state photodetachment notwithstanding, photodetachment microscopy images produced at the excited thresholds could be analysed to provide a measure of these excited-term thresholds with interferometric precision. Starting from the three possible fine-structure sub-levels of P− 3s23p4 3P, the five fine-structure thresholds that may be detected, taking the selection rules into account, have been measured. They are combined with the spectroscopic data available in the literature on neutral P to produce an improved experimental value of the electron affinity eA of phosphorus: 602 179(8) m−1 or 0.746 607(10) eV. Taking all covariances of the optimized energy levels into account, one can merge them with the former measure of the three lowest detachment thresholds of P−, which results in a slightly more precise value of eA(P): 602 181(8) m−1, or 0.746 609(9) eV. The accuracy of eA(P) is now essentially limited by the uncertainty on the 2Do3/2 and 2Do5/2 energy levels of the neutral atom. The fine-structure intervals of the 3s23p3 2Do doublet of the neutral atom and of the 3s23p4 3P triplet of the negative ion have their accuracy improved by more than one order of magnitude.

Zeeman effect of the 6011 Å line of Pr3+: LaCl3 using the fluorescence line-narrowing technique

Eur. Phys. J. D 5, 207–216 (1999)The formula (9) was erroneous. The exponent of the numerical factor should be 2/3 instead of 3/2, and whole formula should read

Three-Photon Detachment of Iodine Negative Ions

Abstract The Zeeman effect of the 6011 A resonance line of Pr 3+ in a LaCl 3 crystal has been studied by means of the fluorescence line-narrowing technique using a cw single-mode tunable laser. The experiments have confirmed the assumptions made previously to interpret the spectra in zero magnetic field. They have led to accurate values of the hyperfine structure constant and of the spectroscopic splitting g -factor of the ground level.

Three-step laser spectroscopy and multichannel quantum defect analysis of odd-parity Rydberg states of neutral ytterbium

I- ions formed in an ionic beam from a hot cathode discharge source are submitted to the intense light pulse of a 1.064 μm Nd:YAG laser. The neutral atoms produced by three-photon detachment are detected. Varying the laser pulse energy and recording the corresponding variation of the detachment signal makes obvious the saturation of the three-photon process. This observation gives an approximate value of the generalized cross-section, σ = 1.5 10-37 s-1 W-3 m6.

Lifetimes of Rydberg levels in the perturbed 6snd 1,3D2 series of barium I

High-lying odd-parity levels of neutral ytterbium are investigated by the method of selective three-step laser spectroscopy. Excitation from the ground state 4f146s2 is performed by means of three dye lasers and the Rydberg levels are detected by using the field ionisation method. Three different levels are used as starting levels of the transitions to Rydberg levels. Thus Rydberg levels pertaining to 6snp J=0-2 and 6snf J=2, 3 series as well as some 4f135d26s levels are observed. The new experimental data are analysed by means of the multichannel quantum defect theory. The theoretical analysis consists of a J by J parametrisation of the observed energy spectra. The perturbations of the Rydberg series 6snp J=1, 6snp 3P0 and 6snf J=3 by levels of the 4f135d26s configuration are clearly interpreted. The limitations of the MQDT models derived solely from energy data are discussed. A revised value of the first ionisation limit is proposed.