Observation of thresholds and overlapping resonances below the 102P1/2and2P

Abstract

A collinear beam apparatus has been used to study photodetachment of Cs − . Partial cross sections were measured using state-selective detection based on a resonance ionization scheme. Several resonances were observed in the Cs(10 2 S), Cs(6 2 F ), Cs(6 2 G), and Cs(6 2 H ) final-state channels below the Cs(10 2 P 3/2 ) channel opening. A model was developed to account for the interference between overlapping resonances. This model is essentially a generalization of the Fano [U. Fano, Phys. Rev. 124, 1866(1961] and Shore [ B. W. Shore, Phys. Rev. 171, 43 (1968)] parametrizations for single resonances. Resonance parameters were extracted by fitting the model to the data sets. The openings of the Cs(10 2 S) and Cs(6 2 F ) channels, where the polarizabilities of the atomic states are large and positive, showed rapid onsets. In the case of the Cs(6 2 G) and Cs(6 2 H ) channels, on the other hand, the photodetachment cross sections increased slowly with energy. For the Cs(6 2 H ) channel this is the expected behavior, since it is the result of a large and negative polarizability of the 6 2 H state. In addition, the excitation of the Cs(6 2 H ) state with respect to the Cs ground state was found to be 28 356.3(2) cm −1 , in agreement with a previous experiment.

Extreme Correlation and Repulsive Interactions in Highly Excited Atomic Alkali Anions

“…Fig. 4b shows the same channels in cesium along with measured results [34]. No previous calculations of these states exist.…”

“…One compelling question is if this dipole structure is present in non-hydrogenic atoms, since the non-penetrating high-l states rarely interact with the core and become nearly degenerate. Many parallels between hydrogen and lithium have been observed at higher (n ≥ 4) thresholds [29][30][31], but with other atoms largely unexplored.Recently, the GUNILLA group at the University of Gothenburg measured PCSs for photodetachment into very excited channels: 7s, 5f , and 5g in potassium, 5g in sodium, and 10s, 6f , 6g, and 6h in cesium [21,[32][33][34]. These observations highlighted the dramatic role of the long-range interaction between the photodetached electron and the highly polarizable atom, especially in the unusual scenario involving repulsive interactions.…”

“…Recently, the GUNILLA group at the University of Gothenburg measured PCSs for photodetachment into very excited channels: 7s, 5f , and 5g in potassium, 5g in sodium, and 10s, 6f , 6g, and 6h in cesium [21,[32][33][34]. These observations highlighted the dramatic role of the long-range interaction between the photodetached electron and the highly polarizable atom, especially in the unusual scenario involving repulsive interactions.…”

“…FIG.4. Observed[34] (round dots) and calculated PCSs for a) potassium and b) cesium. PCSs for the 6f (black, dashed line), 6g (blue, square dots), and 6h (red, solid) are shown.…”

Determination of the dipole polarizability of the alkali-metal negative ions

“…Electron affinities (EAs) of these systems have been measured very precisely [3][4][5][6][7]. Photoabsorption spectra of these ions have also been extensively investigated both theoretically and experimentally, in order to understand their structures [8][9][10][11]. Starting from seventies, a series of studies on the photodetachment of negative lithium (Li − ), sodium (Na − ) and potassium (K − ) ions have been conducted by several groups [5,[12][13][14][15].…”