A sensitive photoabsorption technique for studies of gas-phase biomolecules has been used at the ELISA electrostatic heavy-ion storage ring. We show that the anion form of the chromophore of the green fluorescent protein in vacuo has an absorption maximum at 479 nm, which coincides with one of the two absorption peaks of the protein. Its absorption characteristics are therefore ascribed to intrinsic chemical properties of the chromophore. Evidently, the special beta-can structure of the protein provides shielding of the chromophore from the surroundings without significantly changing the electronic structure of the chromophore through interactions with amino acid side chains.

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The magnetic-dipole transition probabilities between the fine-structure levels (1s^2 2s^2 2p) ^2P_1/2 - ^2P_3/2 for B-like ions and (1s^2 2s 2p) ^3P_1 - ^3P_2 for Be-like ions are calculated. The configuration-interaction method in the Dirac-Fock-Sturm basis is employed for the evaluation of the interelectronic-interaction correction with negative-continuum spectrum being taken into account. The 1/Z interelectronic-interaction contribution is derived within a rigorous QED approach employing the two-time Green function method. The one-electron QED correction is evaluated within framework of the anomalous magnetic-moment approximation. A comparison with the theoretical results of other authors and with available experimental data is presented

Over a period of eight months, we have monitored transition frequencies between nearly degenerate, opposite-parity levels in two isotopes of atomic dysprosium (Dy). These transition frequencies are highly sensitive to temporal variation of the fine-structure constant (α) due to relativistic corrections of large and opposite sign for the opposite-parity levels. In this unique system, in contrast to atomic-clock comparisons, the difference of the electronic energies of the opposite-parity levels can be monitored directly utilizing a radio-frequency (rf) electric-dipole transition between them. Our measurements show that the frequency variation of the 3.1-MHz transition in 163 Dy and the 235-MHz transition in 162 Dy are 9.0±6.7 Hz/yr and -0.6±6.5 Hz/yr, respectively. These results provide a value for the rate of fractional variation of α of (−2.7 ± 2.6) × 10 −15 yr −1 (1 σ) without any assumptions on the constancy of other fundamental constants, indicating absence of significant variation at the present level of sensitivity.

In this Letter, we report a new mass for 11Li using the trapping experiment TITAN at TRIUMF's ISAC facility. This is by far the shortest-lived nuclide, t_{1/2}=8.8 ms, for which a mass measurement has ever been performed with a Penning trap. Combined with our mass measurements of ;{8,9}Li we derive a new two-neutron separation energy of 369.15(65) keV: a factor of 7 more precise than the best previous value. This new value is a critical ingredient for the determination of the halo charge radius from isotope-shift measurements. We also report results from state-of-the-art atomic-physics calculations using the new mass and extract a new charge radius for 11Li. This result is a remarkable confluence of nuclear and atomic physics.

Recent high-precision mass measurements of 9 Li and 9 Be, performed with the TITAN Penning trap at the TRIUMF ISAC facility, are analyzed in light of state-of-the-art shell model calculations. We find an explanation for the anomalous Isobaric Mass Multiplet Equation (IMME) behaviour for the two A = 9 quartets. The presence of a cubic d = 6.3(17) keV term for the J π = 3/2 − quartet and the vanishing cubic term for the excited J π = 1/2 − multiplet depend upon the presence of a nearby T = 1/2 state in 9 B and 9 Be that induces isospin mixing. This is contrary to previous hypotheses involving purely Coulomb and charge-dependent effects. T = 1/2 states have been observed near the calculated energy, above the T = 3/2 state. However an experimental confirmation of their J π is needed.PACS numbers: 21.10. Dr,21.10.Hw,27.20.+n Atomic nuclei are described by their binding energy and three quantum numbers: the total angular momentum J, parity π, and isospin T . This framework allows one to identify, each of the ∼ 3000 observed nuclei [1] unambiguously. The isospin quantity is analogous to spin and was first introduced by Heisenberg [2] to describe the charge-independence of the nuclear force. Within the isospin formalism, neutrons (n) and protons (p) are nucleons of isospin T = 1/2 but distinguished by different z-projections T z (n) = 1/2 and T z (p) = -1/2 [2,3]. Nuclei with the same mass number A, total angular momentum and parity form multiplets where the individual members have a projection T z = (N − Z)/2. Assuming isospin is a good quantum number, members of an isobaric multiplet have identical properties. However, Weinberg and Treiman [4] noted that the mass excess ∆ (which is a measure of the nuclear binding energy and defined as the difference between the atomic mass and the atomic mass number) of such nuclides were not identical, but were rather laying along a parabola:where a, b, c are coefficients that depend on all quantum numbers except T z . This so-called isobaric multiplet mass equation (IMME) has proven to be a powerful tool to predict unknown masses. For instance, it is used to obtain masses of nuclei along the rapid proton capture path, where most of the masses are not well known [5] or to provide detailed mass values, which are experimentally inaccessible due to half-life and productions constraints [6]. Recently, the precise mass measurement of 12 Be [7] using the TITAN (TRIUMF Ion Traps for Atomic and Nuclear science) Penning trap mass spectrometer [8,9] has been used as a solid anchor point together with the IMME to address the ambiguous spin assignment of T = 2 states in 12 C and 12 Be.Several tests of the IMME were performed and for most cases, it has followed the original quadratic behaviour [10]. However, in some cases, large deviations were discovered and the incorporation of cubic d(A, T )T [17,18] quintets. The unveiling of the non-quadratic behaviour of the A = 32 and 33 multiplets was only possible due to the precise and accurate mass measurement of some of its members, at the δm/m ∼...

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TITAN (TRIUMF's Ion Traps for Atomic and Nuclear science) is an online facility designed to carry out high-precision mass measurements on singly and highly charged radioactive ions. The TITAN Penning trap has been built and optimized in order to perform such measurements with an accuracy in the sub ppb-range. A detailed characterization of the TITAN Penning trap is presented and a new compensation method is derived and demonstrated, verifying the performance in the range of sub-ppb.