Speaker
Description
Metastable levels are responsible for parity forbidden lines occurring in many low-density astrophysical plasmas, found in e.g gaseous nebulae, planetary nebulae, protostars, stellar chromospheres. Line ratios from forbidden lines are a reliable tool for diagnostics of temperature and density of low-density astronomical objects.
We have applied the laser probe technique [1] to singly ionized iron (Fe II) in the ion storage ring facility at the DESIREE laboratory [2]. The lifetimes of four metastable state were measured with about 10 % accuracy. In combination with branching fractions obtained from astrophysical spectra the transition probabilities will be determined.
Figure 1: A sketch showing the arrangement of the energy levels used for the probing technique and the wavelengths of the laser and fluorescence signals (left), and the ion storage ring and the detection scheme used at DESIREE (right).
We have demonstrated the successful measurement of the lifetime for the metastable states of a complex ion at DESIREE by the application of laser probing technique. We will report the measured lifetime data for four $3d^64s~b^4F$ levels.
Acknowledgements: U.B. and A.C. acknowledge the support by the Latvian Council of Science, Fundamental and Applied Research Project No. lzp-2023/1-0199: “The Laser Photodetachment Spectroscopy on Negative Ions”.
[1] S Mannervik et al 2005 Phys. Scr. 49 (2005)
[2] Schmidt H. T., et all., Review of Scientific Instruments 84, 055115 (2013)
