A laser probing method has been used in an ion storage ring to measure the lifetimes of the metastable and levels in . The lifetimes obtained were s for and s for . The most accurate results from ion trap measurements differ by 10% from each other. Our value for supports the longer lifetime value reported from Werth's group. For the level, the new measurement is consistent with previous results.

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We report on experimental transition probabilities for thirteen forbidden [Fe II] lines originating from three different metastable Fe  levels. Radiative lifetimes have been measured of two metastable states by applying a laser probing technique on a stored ion beam. Branching ratios for the radiative decay channels, i.e. M1 and E2 transitions, are derived from observed intensity ratios of forbidden lines in astrophysical spectra and compared with theoretical data. The lifetimes and branching ratios are combined to derive absolute transition probabilities, A-values. We present the first experimental lifetime values for the two Fe II levels a 4 G 9/2 and b 2 H 11/2 and A-values for 13 forbidden transitions from a 6 S 5/2 , a 4 G 9/2 and b 4 D 7/2 in the optical region. A discrepancy between the measured and calculated values of the lifetime for the b 2 H 11/2 level is discussed in terms of level mixing. We have used the code CIV3 to calculate transition probabilities of the a 6 D-a 6 S transitions. We have also studied observational branching ratios for lines from 5 other metastable Fe II levels and compared them to calculated values. A consistency in the deviation between calibrated observational intensity ratios and theoretical branching ratios for lines in a wider wavelength region supports the use of [Fe II] lines for determination of reddening.