# Electron-impact excitation of the (4p55s5p) 4S3/2 quasimetastable state in Rb

V Roman, S. Demes

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V Roman, S. Demes. Electron-impact excitation of the (4p55s5p) 4S3/2 quasimetastable state in Rb. XXXI International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015), Jul 2019, Deauville, France. pp.132012, 10.1088/1742-6596/1412/13/132012. [hal-03383342](https://hal.science/hal-03383342)

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# Electron-impact excitation of the (4p$^5$5s5p)$^4$S$_{3/2}$ quasimetastable state in Rb

To cite this article: V Roman and S Demes 2020 *J. Phys.: Conf. Ser.* **1412** 132012

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# Electron-impact excitation of the (4p⁵s5p)⁴S₃/₂ quasimetastable state in Rb

V Roman<fnref n="1" />* and S Demes<fnref n="2" />

**Synopsis** The ejected-electron excitation function of the (4p⁵s5p)⁴S₃/₂ quasimetastable state in rubidium was experimentally investigated by electron-impact in the energy range from the excitation threshold at 16.64 eV to 100 eV. The obtained data at 0.12 eV energy resolution indicate the presence of negative-ion resonances just above excitation threshold. A comparison is made with the optical excitation function of the (4p⁵s5p)⁴S₃/₂ → (4p⁶5p)²P₃/₂ transition (λ = 82.37 nm), measured earlier with a lower energy resolution of ≈1.5 eV.

It is known that in alkali atoms (K, Rb, Cs) there is a subclass of p⁶-core excited quartet states which is due to the mixing with doublet states of the same total electronic angular momentum *J* possess both radiative and electronic decay channels [1]. As a rule, the radiative decay dominates for such quasimetastable states, while autoionization probability remains small. The latter makes difficult the experimental observation of quasimetastable states in ejected-electron spectra [2]. The optical excitation function for the (4p⁵s5p)⁴S₃/₂ → (4p⁶5p)²P₃/₂ transition (λ = 82.37 nm) in Rb was measured earlier with an incident-electron energy resolution of ≈1.5 eV [3]. In the present work we obtained the ejected-electron excitation function of the (4p⁵s5p)⁴S₃/₂ state with an improved 0.12 eV energy resolution by using energy-selective electron beam and by accurate measurement of the ejected-electron spectra in a broad impact energy range.

The apparatus and the experimental procedure were described in details earlier [4]. The ejected-electron spectra were measured at 54.7° observation angle. Due to the overlapping of the ⁴S₃/₂ line with the high intensity neighboring line (4p⁵d5s)⁴P₁/₂ with 16.69 eV excitation threshold, the total relative uncertainty is approximately 40% for the most of our data.

Figure 1 shows the measured ejected-electron excitation function of the (4p⁵s5p)⁴S₃/₂ state and the optical excitation function for λ = 82.37 nm [3] in an impact-energy range from the 16.64 eV excitation threshold up to 100 eV. Our comparison shows that there is a fairly good agreement between the two types of data. Due to the better energy resolution of the present measurements, the “fine” structure *a*-*b* is clearly seen in the ejected-electron function just above the excitation threshold. The broad

<figure><img src="image_3.png" /><figcaption>**Figure 1.** The electron-impact excitation functions of the (4p⁵s5p)⁴S₃/₂ state in rubidium: ● - present data; ○ - optical data [3]. The inset shows the threshold region of the present data. The data [3] and our data are normalized with incident-electron energy of 65 eV.</figcaption></figure>

maximum *c* in our data [3] corresponds to the spin-exchange character of the electronic excitation of the ⁴S₃/₂ state. The notable scatter of experimental data, which is observed between 20 and 25 eV in the ejected-electron excitation function could reflect the combined effect of several overlapping resonances.

In order to obtain the absolute values of the excitation cross sections for the (4p⁵s5p)⁴S₃/₂ and other p⁶-core excited states in rubidium, we have performed relativistic distorted-wave calculations.

## References

[1] Mendelson A *et al* 1987 *Phys. Rev. A*. **35** 2095

[2] Borovik A *et al* 2006 *Phys. Rev. A*. **73** 062701

[3] Bogachev G 1974 *Ukr. Phys. J.* **12** 2061

[4] Borovik A *et al* 2005 *J. Phys. B* **38** 1081

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<footnote n="1">¹Institute of Electron Physics, National Academy of Sciences of Ukraine, Uzhgorod, 88017, Ukraine</footnote>

<footnote n="2">²Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, 4026, Hungary</footnote>

<footnote>* E-mail: viktoriyaroman11@gmail.com</footnote>