4d and 5p photoabsorption in laser-produced thulium plasmas
| Autor: | M. Mahmoad, G O'Sullivan, Elaine Long, Paddy Hayden, N. Krstulovic, Padraig Dunne, Emma Sokell, Robert Stefanuik |
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| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | Physical Review A. 101 |
| ISSN: | 2469-9934 2469-9926 |
| Popis: | The dual-laser plasma method has been used to record photoabsorption spectra of Tm, $\mathrm{T}{\mathrm{m}}^{+}$, and $\mathrm{T}{\mathrm{m}}^{2+}$ ions. The dominant process is $4d$ photoexcitation, giving rise to structure in the 140--240-eV region while structure due to $5p$ excitation is observed in the 27--38-eV region. Due to successive removal of $6s$ electrons outside a $4{f}^{13}$ core with increasing ionization, the $4d$ photoabsorption spectra of Tm, $\mathrm{T}{\mathrm{m}}^{+}$, and $\mathrm{T}{\mathrm{m}}^{2+}$ are very similar. The spectrum of neutral thulium shows autoionizing resonances, excited from both fine-structure levels of the $4{f}^{13}6{s}^{2}$ ground state, evidenced by a clear double-peaked Fano structure in the 140--240-eV range. Similar features are observed and can be associated with $4d\text{\ensuremath{-}}4f$ transitions in $\mathrm{T}{\mathrm{m}}^{+}$ and $\mathrm{T}{\mathrm{m}}^{2+}$. Broad structure, distinctly different from the spectra of Tm, $\mathrm{T}{\mathrm{m}}^{+}$, and $\mathrm{T}{\mathrm{m}}^{2+}$, in the same $4d\text{\ensuremath{-}}4f$ region of the spectrum at 25 ns suggests that $\mathrm{T}{\mathrm{m}}^{3+}$, with a different number of $4f$ electrons, may be present in the absorbing plasma immediately after its formation. Significant broadening due to autoionization was observed in the $5p$ absorption region for all three ion stages. The observed transitions were identified with the aid of the cowan suite of codes, which are based on Hartree-Fock with configuration interaction approach. |
| Databáze: | OpenAIRE |
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