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Papers by B. Birkett

Research paper thumbnail of Lifetime Measurements of Metastable States in He-like Heavy Ions

Research paper thumbnail of Hyperfine quenching and precision measurement of the 2 ^{3}P_{0}-2 ^{3}P_{1} fine-structure splitting in heliumlike gadolinium (Gd^{62+})

ABSTRACT The hyperfine-quenched transition 23P0-11S0 has been observed in heliumlike gadolinium (... more ABSTRACT The hyperfine-quenched transition 23P0-11S0 has been observed in heliumlike gadolinium (Gd62+) in the two isotopes 155Gd and 157Gd. The lifetime for the transition (tau0) has been measured for each isotope and found to be tau0(155)=13.43(27)×10-12 sec and tau0(157)=7.65(55)×10-12 sec. From the measured lifetimes a value is inferred for the absolute value of the 23P0-23P1 fine-structuring splitting ||DeltaE0-1|| in Gd62+ with the result ||DeltaE0-1||=18.57(19) eV, where the error represents 1 standard deviation. This result is compared with calculations based on the multiconfiguration Dirac-Fock method and on the unified method.

Research paper thumbnail of Nuclear magnetization distribution radii determined by hyperfine transitions in the 1s level of H-like ions ^{185}Re^{74+} and ^{187}Re^{74+}

Physical Review A, 1998

The Fϭ3 to Fϭ2 hyperfine transitions in the 1s ground state of the two isotopes 185 Re 74ϩ and 18... more The Fϭ3 to Fϭ2 hyperfine transitions in the 1s ground state of the two isotopes 185 Re 74ϩ and 187 Re 74ϩ were measured to be (4560.5Ϯ3) Å and (4516.9Ϯ3) Å, respectively, using emission spectroscopy in an electron beam ion trap. After applying appropriate corrections for the nuclear charge distribution and QED effects, a Bohr-Weisskopf effect of ϭ2.23͑9͒% and 2.30͑9͒% are found for 185 Re and 187 Re, respectively. This value is almost twice that of a previous theoretical estimate, and indicates a distribution of the nuclear magnetization far more extended than that of the nuclear charge. A radius of the magnetization distribution of ͗r m 2 ͘ 1/2 ϭ7.57(32) fm and ͗r m 2 ͘ 1/2 ϭ7.69͑32͒ fm for 185 Re and 187 Re, respectively, is inferred from the data.

Research paper thumbnail of Hyperfine quenching and measurement of the 2 ^{3}P_{0}–2 ^{3}P_{1} fine-structure splitting in heliumlike silver (Ag^{45+})

Physical Review A, 1993

The hyperfine-quenched transition 2 3P0-1 1S0 has been observed in heliumlike silver (Ag45+) in t... more The hyperfine-quenched transition 2 3P0-1 1S0 has been observed in heliumlike silver (Ag45+) in the two isotopes 107Ag and 109Ag. The lifetime for the transition has been measured for each isotope and found to be tau0(107)=3.98(37)×10-12 sec and tau0(109)=2.84(32)×10-12 sec. From the measured lifetimes a value is inferred for the absolute value of the 2 3P0-2 3P1 fine-structure splitting ||DeltaE0-1|| in Ag45+ with the result ||DeltaE0-1||=0.79(04) eV, where the uncertainty is the experimental uncertainty taken at the 1sigma confidence level. This result is compared with calculations based on the multiconfigurational Dirac-Fock method, the unified method, and recent results from the relativistic configuration-interaction method.

Research paper thumbnail of Cascade-free Doppler-tuned precision measurement of the lifetime of the 2 ^{3}S_{1} state in He-like niobium (^{93}Nb^{39+})

Physical Review A, 1994

... 3. This filter-ing procedure produced remarkably pure 2 'S lines at each positio... more ... 3. This filter-ing procedure produced remarkably pure 2 'S lines at each position of the movable detector, so that a single exponential without any background could be fit excep-tionally well to the data. ... [2] RW Dunford, DA Church, CJ Liu, HG Berry, ML Raphaelian, M. Hass ...

Research paper thumbnail of n=2 to n=1 forbidden transitions in H-like and He-like silver and niobium

Physical Review A, 1993

We report on beam-foil time-of-Aight measurements of forbidden transitions in H-like and He-like ... more We report on beam-foil time-of-Aight measurements of forbidden transitions in H-like and He-like Nb and Ag. The lifetimes of the 2 'So state of He-like Nb, the 2s, &2 state of H-like Ag, and the 2 P, state of He-like Ag have been measured with precisions ranging from 1.7% to 10%. These are the highest-Z ions for which these lifetimes have been measured.

Research paper thumbnail of Lifetime Measurements of Metastable States in He-like Heavy Ions

Research paper thumbnail of Hyperfine quenching and precision measurement of the 2 ^{3}P_{0}-2 ^{3}P_{1} fine-structure splitting in heliumlike gadolinium (Gd^{62+})

ABSTRACT The hyperfine-quenched transition 23P0-11S0 has been observed in heliumlike gadolinium (... more ABSTRACT The hyperfine-quenched transition 23P0-11S0 has been observed in heliumlike gadolinium (Gd62+) in the two isotopes 155Gd and 157Gd. The lifetime for the transition (tau0) has been measured for each isotope and found to be tau0(155)=13.43(27)×10-12 sec and tau0(157)=7.65(55)×10-12 sec. From the measured lifetimes a value is inferred for the absolute value of the 23P0-23P1 fine-structuring splitting ||DeltaE0-1|| in Gd62+ with the result ||DeltaE0-1||=18.57(19) eV, where the error represents 1 standard deviation. This result is compared with calculations based on the multiconfiguration Dirac-Fock method and on the unified method.

Research paper thumbnail of Nuclear magnetization distribution radii determined by hyperfine transitions in the 1s level of H-like ions ^{185}Re^{74+} and ^{187}Re^{74+}

Physical Review A, 1998

The Fϭ3 to Fϭ2 hyperfine transitions in the 1s ground state of the two isotopes 185 Re 74ϩ and 18... more The Fϭ3 to Fϭ2 hyperfine transitions in the 1s ground state of the two isotopes 185 Re 74ϩ and 187 Re 74ϩ were measured to be (4560.5Ϯ3) Å and (4516.9Ϯ3) Å, respectively, using emission spectroscopy in an electron beam ion trap. After applying appropriate corrections for the nuclear charge distribution and QED effects, a Bohr-Weisskopf effect of ϭ2.23͑9͒% and 2.30͑9͒% are found for 185 Re and 187 Re, respectively. This value is almost twice that of a previous theoretical estimate, and indicates a distribution of the nuclear magnetization far more extended than that of the nuclear charge. A radius of the magnetization distribution of ͗r m 2 ͘ 1/2 ϭ7.57(32) fm and ͗r m 2 ͘ 1/2 ϭ7.69͑32͒ fm for 185 Re and 187 Re, respectively, is inferred from the data.

Research paper thumbnail of Hyperfine quenching and measurement of the 2 ^{3}P_{0}–2 ^{3}P_{1} fine-structure splitting in heliumlike silver (Ag^{45+})

Physical Review A, 1993

The hyperfine-quenched transition 2 3P0-1 1S0 has been observed in heliumlike silver (Ag45+) in t... more The hyperfine-quenched transition 2 3P0-1 1S0 has been observed in heliumlike silver (Ag45+) in the two isotopes 107Ag and 109Ag. The lifetime for the transition has been measured for each isotope and found to be tau0(107)=3.98(37)×10-12 sec and tau0(109)=2.84(32)×10-12 sec. From the measured lifetimes a value is inferred for the absolute value of the 2 3P0-2 3P1 fine-structure splitting ||DeltaE0-1|| in Ag45+ with the result ||DeltaE0-1||=0.79(04) eV, where the uncertainty is the experimental uncertainty taken at the 1sigma confidence level. This result is compared with calculations based on the multiconfigurational Dirac-Fock method, the unified method, and recent results from the relativistic configuration-interaction method.

Research paper thumbnail of Cascade-free Doppler-tuned precision measurement of the lifetime of the 2 ^{3}S_{1} state in He-like niobium (^{93}Nb^{39+})

Physical Review A, 1994

... 3. This filter-ing procedure produced remarkably pure 2 'S lines at each positio... more ... 3. This filter-ing procedure produced remarkably pure 2 'S lines at each position of the movable detector, so that a single exponential without any background could be fit excep-tionally well to the data. ... [2] RW Dunford, DA Church, CJ Liu, HG Berry, ML Raphaelian, M. Hass ...

Research paper thumbnail of n=2 to n=1 forbidden transitions in H-like and He-like silver and niobium

Physical Review A, 1993

We report on beam-foil time-of-Aight measurements of forbidden transitions in H-like and He-like ... more We report on beam-foil time-of-Aight measurements of forbidden transitions in H-like and He-like Nb and Ag. The lifetimes of the 2 'So state of He-like Nb, the 2s, &2 state of H-like Ag, and the 2 P, state of He-like Ag have been measured with precisions ranging from 1.7% to 10%. These are the highest-Z ions for which these lifetimes have been measured.

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