The role of cascade processes in electron-impact excitation of the (3p⁵4s²)²P_{3/2, 1/2}autoionizing levels in potassium

Abstract

The cascade population of the (3p54s2)2P3/2, 1/2 lowest autoionizing levels in potassium has been studied to shed light on recent experimental observations of a noticeable enhancement in the cross sections around 22 eV incident electron energy. The ejected-electron excitation functions of both levels have been re-measured in the range of 20–28 eV, and calculations of the decay parameters for the 3p54s4p levels have been performed in single-configuration Hartree–Fock and configuration-interaction approaches. The analysis of these results, together with other available experimental and theoretical data on the 3p subshell excitation in potassium, revealed a relatively small contribution (<3%) of radiative transitions from the (3p5 4s4p1P)2P, 2D levels to the apparent (including cascade contributions) excitation cross sections of the (3p54s2)2P3/2, 1/2 levels. However, the decay of negative-ion resonances associated with the upper doublets in the 3p54s4p and 3p53d4s configurations may lead to a significant cascade population of the (3p54s2)2P3/2, 1/2 levels in the impact energy region 21–28 eV.

Atomic Data for Zn Ii: Improving Spectral Diagnostics of Chemical Evolution in High-Redshift Galaxies

“…The most inclusive description of the adopted approach is given by Bogdanovich (2004Bogdanovich ( , 2005, whereas its application for data production and their accuracy analysis is given by Bogdanovich & Martinson (1999), Bogdanovich et al (2003aBogdanovich et al ( , 2003b, , and Kupliauskienė et al (2006).…”

The 4p6-core excited autoionising states in strontium: Classification and excitation dynamics

“…Moreover, an abrupt rise of the cross-section above the thresholds of features E, F, G and an evident resonance shape of features E and F all point out an important role of negative-ion resonances (reaction (3)) in excitation of the cascading levels. Note that such 'resonance' cascades were earlier observed in electron impact excitation of low-lying autoionising states in lithium [14] and potassium [17] atoms.…”

“…But, for the lowest coreexcited levels of Na [16] and K [17], a better agreement was noticed between experimental excitation energies and those of single-configuration Hatree-Fock rather than the large scale configuration interaction results. It happened due to the cancellation of correlation contributions in the initial and final states.…”

Radiative transitions between lowest autoionizing states in sodium

“…obtained by using the balance equations for three-level system in [16]. In (1), N 1 and N 0 are the population densities of the levels 2p 5 3s3p LSJ and 2p 6 3s 2 S 1/2 , respectively, N e and v are the density and velocity of exciting electrons, σ 01 and σ 02 are the excitation crosssections from the ground states to the 2p 5 3s 2 2 P J0 and 2p 5 3s3p LSJ levels, respectively, A 10 and A a 1 are radiative and autoionization probabilities from the states 2p 5 3s 2 2 P J0 , respectively, and γ 21 is the fluorescence yield of the transition 2p 5 3s3p LSJ → 2p 5 3s 2 2 P J0 .…”

“…The theoretical investigation of the energies and radiative transition probabilities in Na atom is performed by using the method fully described and successfully applied in our previous papers [16][17][18][19][20][21][22][23]. While calculating the energy spectra, the relativistic effects were taken into account within the traditional Breit-Pauli approximation, i. e. the spin-orbit and other relativistic one-and two-electron interactions accurate up to the square of the fine structure constant were included.…”