Comparison of theory and experiment for radiative characteristics in neutral thulium

Intensities in the Tm i emission series originating from a common upper level are measured using a Fourier transform spectrometer. The derived relative transition probabilities within each series are compared to the theoretical predictions obtained from large-scale calculations that combine configuration interaction with many-body perturbation theory. Moreover, the Tm i spectrum recorded in an external magnetic field is analyzed. Our theoretical results well describe the current measurements and show no more than a two-fold difference from previous experimental data on absolute transition probabilities. Additionally, Landé $g$ factors, hyperfine structure constants, and atomic electric quadrupole moments for several levels of interest are computed and compared to experimental observations, where available.

Figure 1

Examples of intensity determination of the hyperfine components for the lines from the upper level with energy $35682.251$ ${\mathrm{cm}}^{-1}$ $({\left(4f^{12}5d6s6p\right)}_{7/2}^o$): (a) line $17929.612$ ${\mathrm{cm}}^{-1}$; (b) line $16844.863$ ${\mathrm{cm}}^{-1}$; blue lines: experiment, orange lines: simulated line profile; vertical bars: respective intensity of hyperfine components.

Figure 2

Odd- (black) and even-parity (red) levels in Tm i with energies up to 36000 ${\mathrm{cm}}^{-1}$ according to the NIST ASD [50].

Figure 3

Comparison of experimental and theoretical intensity distributions of emission lines originating from a common upper level at energies (a) $32217.195$ ${\mathrm{cm}}^{-1}$, (b) $33943.282$ ${\mathrm{cm}}^{-1}$, and (c) $35682.251$ ${\mathrm{cm}}^{-1}$.

Figure 4

Recorded transition between the levels ${\left(4f^{13}{(}^2{F}_{7/2}^o)6s7s{(}^3{S}_1)\right)}_{9/2}^o$ at $32217.195$ ${\mathrm{cm}}^{-1}$ and ${\left(4f^{13}{(}^2{F}_{7/2}^o)6s6p{(}^3{P}_1^o)\right)}_{9/2}$ at $17613.659$ ${\mathrm{cm}}^{-1}$. Top: without an external magnetic field; middle: $\pi$ component in the external magnetic field of 1820 G; bottom: $\sigma$ component in the external magnetic field of 1820 G. The amplitude of the experimental signal is normalized to the theory.