Experimental studies of partial photodetachment cross sections in K−below the K(7 2P) threshold

Abstract

A collinear beams apparatus has been used to determine photodetachment cross sections for K − in the photon energy range 4.250-4.360 eV. State-selective detection, utilizing a resonance ionization scheme, was applied to measure partial cross sections for those channels which leave the residual K atoms in the excited 7 2 S, 5 2 F , and 5 2 G states. The energy region studied encompassed the openings of the aforementioned channels, as well as the channel that leaves the K atom in the 7 2 P state. Two previously unobserved resonances were seen in all three partial cross sections between the K(5 2 G) and K(7 2 P ) thresholds. It is shown that a more reliable determination of resonance parameters can be made if the same resonances are observed in several channels. In the region below the K(5 2 F ) threshold, three previously observed resonances were investigated [Kiyan et al., Phys. Rev. Lett. 84, 5979 (2000)]. A greatly increased modulation of the signal was obtained by detecting in the K(7 2 S) channel instead of the K(5 2 S) channel used in the previous study. Furthermore, the shapes of the cross sections in the threshold regions are discussed. A detailed description of the apparatus and the experimental procedure employed is presented in the paper.

Observation of thresholds and overlapping resonances below the 102P1/2and2PLindahl1, Rohlén2, Hultgren3 et al. 2013Phys. Rev. ASelf Cite5050View full textAdd to dashboardCite

“…2. The experimental arrangement has been described in detail in a recent publication [16]. Negative ions of cesium were produced in a cesium sputter ion source using a solid aluminium target.…”

“…The positive ions were detected by the position-sensitive detector. The inhomogeneous field in the field ionizer helped to separate the signal from the major source of background, namely, positive ions created in the interaction region by sequential photodetachment-photoionization by two uv photons [16].…”

“…Previous experimental investigations of doubly excited states of alkali-metal negative ions include studies on Li − [12,13], Na − [14], K − [15,16], Rb − [17,18], and Cs − [17,19].…”

Extreme Correlation and Repulsive Interactions in Highly Excited Atomic Alkali Anions

“…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.…”