Broken-Symmetry Unrestricted Hybrid Density Functional Calculations on Nickel Dimer and Nickel Hydride

In the present work we investigate the adequacy of broken-symmetry unrestricted density functional theory (DFT) for constructing the potential energy curve of nickel dimer and nickel hydride, as a model for larger bare and hydrogenated nickel cluster calculations. We use three hybrid functionals: the popular B3LYP, Becke's newest optimized functional Becke98, and the simple FSLYP functional (50% Hartree-Fock and 50% Slater exchange and LYP gradient-corrected correlation functional) with two basis sets: all-electron (AE) Wachters+f basis set and Stuttgart RSC effective core potential (ECP) and basis set. We find that, overall, the best agreement with experiment, comparable to that of the high-level CASPT2, is obtained with B3LYP/AE, closely followed by Becke98/AE and Becke98/ECP. FSLYP/AE and B3LYP/ECP give slightly worse agreement with experiment, and FSLYP/ECP is the only method among the ones we studied that gives an unaceptably large error, underestimating the dissociation energy of nickel dimer by 28%, and being in the largest disagreement with the experiment and the other theoretical predictions.Comment: 17 pages, 7 tables, 7 figures; submitted to J. Chem. Phys.; Revtex4/LaTeX2e. v2 (8/5/04): New (and better) ECP results, without charge density fitting (which was found to give large errors). Subtracted the relativistic corrections from all experimental value

Measurement of excited-state transitions in cold calcium atoms by direct femtosecond frequency-comb spectroscopy

We apply direct frequency-comb spectroscopy, in combination with precision cw spectroscopy, to measure the ${\rm 4s4p} ^3P_1 \to {\rm 4s5s} ^3S_1$ transition frequency in cold calcium atoms. A 657 nm ultrastable cw laser was used to excite atoms on the narrow ($\gamma \sim 400$ Hz) ${\rm 4s^2} ^1S_0 \to {\rm 4s4p} ^3P_1$ clock transition, and the direct output of the frequency comb was used to excite those atoms from the ${\rm 4s4p} ^3P_1$ state to the ${\rm 4s5s} ^3S_1$ state. The resonance of this second stage was detected by observing a decrease in population of the ground state as a result of atoms being optically pumped to the metastable ${\rm 4s4p} ^3P_{0,2}$ states. The ${\rm 4s4p} ^3P_1 \to {\rm 4s5s} ^3S_1$ transition frequency is measured to be $\nu = 489 544 285 713(56)$ kHz; which is an improvement by almost four orders of magnitude over the previously measured value. In addition, we demonstrate spectroscopy on magnetically trapped atoms in the ${\rm 4s4p} ^3P_2$ state.Comment: 4 pages 5 figure

Update on the physics of light pseudoscalar mesons

We present an update of the MILC investigation of the properties of light pseudoscalar mesons using three flavors of improved staggered quarks. Results are presented for the $\pi$ and $K$ leptonic decay constants, the CKM matrix element $V_{us}$, the up, down and strange quark masses, and the coefficients of the $O(p^4)$ chiral lagrangian. We have new data for lattice spacing $a \approx 0.15$ fm with several values of the light quark mass down to one-tenth the strange quark mass, higher statistics for $a \approx 0.09$ fm with the light quark mass equal to one-tenth the strange quark mass, and initial results for our smallest lattice spacing, $a \approx 0.06$ fm with light quark mass two-fifths of the strange quark mass.Comment: 7 pages, 4 figures. To be published in Proceedings of Science (Lattice 2006) 163 (2006

The equation of state with nonzero chemical potential for 2+1 flavors

We present results for the QCD equation of state with nonzero chemical potential using the Taylor expansion method with terms up to sixth order in the expansion. Our calculations are performed on asqtad 2+1 quark flavor lattices at $N_t=4$.Comment: Talk given at the XXV International Symposium on Lattice Field Theory, July 30-4 August 2007, Regensburg, German

Baryon masses with improved staggered quarks

The MILC collaboration's simulations with improved staggered quarks are being extended with runs at a lattice spacing of 0.06 fm with quark masses down to one tenth the strange quark mass. We give a brief introduction to these new simulations and the determination of the lattice spacing. Then we combine these new runs with older results to study the masses of the nucleon and the Omega minus in the continuum and chiral limits.Comment: 7 pages, proceedings from Lattice 2007 conferenc

Radiographic Visualization of Arterial Lesions in Cholesterol-Fed Rabbits

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67327/2/10.1177_000331977102200703.pd