The FERRUM project: Experimental transition probabilities from highly excited even 5s levels in Cr ii

Mon. Not. R. Astron. Soc.

et al. 2016

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This work reports new experimental radiative lifetimes of six 3d 2 ( 3 F)5s levels in singly ionized titanium, with an energy around 63 000 cm −1 and four 3d 2 ( 3 F)4p odd parity levels where we confirm previous investigations. Combining the new 5s lifetimes with branching fractions measured previously by Pickering et al., we report 57 experimental log gf values for transitions from the 5s levels. The lifetime measurements are performed using time-resolved laser-induced fluorescence on ions produced by laser ablation. One-and two-step photon excitation is employed to reach the 4p and 5s levels, respectively. Theoretical calculations of the radiative lifetimes of the measured levels as well as of oscillator strengths for 3336 transitions from these levels are reported. The calculations are carried out by a pseudorelativistic Hartree-Fock method taking into account core-polarization effects. The theoretical results are in a good agreement with the experiments and are needed for accurate abundance determinations in astronomical objects.

Section: E X P E R I M E N Tmentioning

confidence: 99%

Oscillator strengths for high-excitation Ti ii from laboratory measurements and calculations

Lundberg

Hartman

Mon. Not. R. Astron. Soc.

et al. 2016

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“…The TR-LIF set-up at Lund High Power Laser Facility is recently described in detail by Engström et al (2014), where a study similar to this, but for Cr , is reported; here we only emphasize the important aspects. The set-up contains two Nd:YAG lasers operating at 10 Hz.…”

Section: Radiative Lifetime Measurementsmentioning

confidence: 90%

The FERRUM project: Experimental lifetimes and transition probabilities from highly excited even 4d levels in Fe ii

Hartman

Nilsson

et al. 2015

A&A

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We report lifetime measurements of the 6 levels in the 3d 6 ( 5 D)4d e 6 G term in Fe  at an energy of 10.4 eV, and f -values for 14 transitions from the investigated levels. The lifetimes were measured using time-resolved laser-induced fluorescence on ions in a laserproduced plasma. The high excitation energy, and the fact that the levels have the same parity as the the low-lying states directly populated in the plasma, necessitated the use of a two-photon excitation scheme. The probability for this process is greatly enhanced by the presence of the 3d 6 ( 5 D)4p z 6 F levels at roughly half the energy difference. The f -values are obtained by combining the experimental lifetimes with branching fractions derived using relative intensities from a hollow cathode discharge lamp recorded with a Fourier transform spectrometer. The data is important for benchmarking atomic calculations of astrophysically important quantities and useful for spectroscopy of hot stars.

“…The experimental set-up for the two-step Time-Resolved Laser Induced Fluorescence (TR-LIF) measurements at the Lund High Power Laser Facility has been described in detail by Engström et al (2014) and Lundberg et al (2016). For an overview, we refer to fig.…”

Section: I F E T I M E M E a S U R E M E N T Smentioning

confidence: 99%

Lifetime measurements and oscillator strengths in singly ionized scandium and the solar abundance of scandium

Rhodin

Belmonte

Monthly Notices of the Royal Astronomical Society

et al. 2017

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The lifetimes of 17 even-parity levels (3d5s, 3d4d, 3d6s and 4p2 ) in the region 57 743-77 837 cm −1 of singly ionized scandium (Sc II) were measured by two-step timeresolved laser induced fluorescence spectroscopy. Oscillator strengths of 57 lines from these highly excited upper levels were derived using a hollow cathode discharge lamp and a Fourier transform spectrometer. In addition, Hartree-Fock calculations where both the main relativistic and core-polarization effects were taken into account were carried out for both low-and high-excitation levels. There is a good agreement for most of the lines between our calculated branching fractions and the measurements of Lawler & Dakin in the region 9000-45 000 cm −1 for low excitation levels and with our measurements for high excitation levels in the region 23 500-63 100 cm −1 . This, in turn, allowed us to combine the calculated branching fractions with the available experimental lifetimes to determine semi-empirical oscillator strengths for a set of 380 E1 transitions in Sc II. These oscillator strengths include the weak lines that were used previously to derive the solar abundance of scandium. The solar abundance of scandium is now estimated to log = 3.04 ± 0.13 using these semi-empirical oscillator strengths to shift the values determined by Scott et al. The new estimated abundance value is in agreement with the meteoritic value (log met = 3.05 ± 0.02) of Lodders, Palme & Gail.