Mirroring Doubly Excited Resonances in Argon

Abstract

New features are revealed in the low-energy photoionization spectrum of Ar by critically combining high photon resolution and differential photoelectron spectroscopic techniques. Two LS-forbidden doubly excited resonances are seen in the 3p(-1)(3/2, 1/2) partial cross sections which exhibit mirroring profiles, resulting in complete cancellation in the total photoionization cross section, as was predicted by Liu and Starace [Phys. Rev. A 59, R1731 (1999)]. These results demonstrate that a new class of weakly spin-orbit induced, mirroring resonances should be observable in partial, but not in total, collisional cross sections involving atoms, molecules, and solids in general.

Partial cross sections of doubly excited helium below the ionization thresholdI7

“…The principal series 6 , 4 n Ј and 7 , 5 n Ј are observed up to the resonances nЈ = 16 and 19, respectively. Note that the resonances 7 , 5 10 and 7 , 5 15 are almost completely suppressed due to interferences with the perturbers 8 , 6 8 and 8,6 9 , respectively. These findings agree well with the results of earlier studies of the total absorption cross sections [2].…”

“…As a result of this mirroring behavior, a resonance that is almost invisible in the TCS ͑ 2 → 0͒ can lead to strong variations in P and Q . This has been shown by CantonRogan and co-workers for two resonances of doubly excited Ar that are extremely weak in the TCS; in the PCSs, however, the resonances are clearly visible [15]. Although 2 → 0 is required for a mirroring behavior to occur, it has been observed in the theoretical photoionization cross section of Li − even for 2 as high as 0.3 [13].…”

New Window Resonances in the Potassium 3sPhotoabsorption Spectrum

“…In particular, the subvalence s-shell photoexcitation in rare gas atoms [5][6][7][8][9][10][11][12][13][14][15] and closely related species [18][19][20][21] have been noted for the window type resonances, appearing as dips in the continuum background of the photo-absorption spectrum. Window resonances are extreme cases of the Beutler-Fano profile with profile index q close to zero.…”

Mirroring and Mimicking of Partial Cross Sections in the Vicinity of a Resonance

“…11 provides a theoretical underpinning to experiment a1 findings that sometimes resonance states that do not appear in total cross sections do appear in partial cross sections. One finds a most recent example in a high-resolution measurement of the low-energy photoionization spectrum of Ar, (15) in which two resonances in the 3p: ,,, partial aoss sections exhibit mirroring profiles, resating in mmplete cancellation in the total photoionization cross section. The near-zero correlationindexes of the resonance states are due to their LS-forbidden character.…”