Observation of an Electric Quadrupole Transition in a Negative Ion: Experiment and Theory.

The first direct experimental observation of an electric quadrupole (E2) absorption transition between bound states of an atomic negative ion has been made. The transition was observed in the negative ion of bismuth by resonant (1+1) photon detachment from Bi^{-} via ^{3}P_{2}→^{3}P_{0} excitation. The E2 transition properties were completely independently calculated using a hybrid theoretical approach to account for the strong multilevel electron interactions and relativistic effects. The experimental and ab initio theoretical results are in excellent agreement, providing valuable new insight into this complex system and forbidden transitions in negative ions more generally.

Search for neutrinos from annihilation of captured low-mass dark matter particles in the sun by super-kamiokande.

Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/c^{2}-200-GeV/c^{2}) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent WIMP-proton cross section for WIMP masses below 200 GeV/c^{2} (at 10 GeV/c^{2}, 1.49×10^{-39} cm^{2} for χχ→bb[over ¯] and 1.31×10^{-40} cm^{2} for χχ→τ^{+}τ^{-} annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent coupling in the few-GeV/c^{2} mass range.

Candidate for laser cooling of a negative ion: observations of bound-bound transitions in La(-).

Despite the tremendous advances in laser cooling of neutral atoms and positive ions, no negatively charged ion has been directly laser cooled. The negative ion of lanthanum, La(-), has been proposed as the best candidate for laser cooling of any atomic anion [ and , Phys. Rev. A 81, 032503 (2010)]. Tunable infrared laser photodetachment spectroscopy is used to measure the bound-state structure of La(-), revealing a spectrum of unprecedented richness with multiple bound-bound electric dipole transitions. The potential laser-cooling transition ((3)F(2)(e)→(3)D(1)(o)) is identified and its excitation energy is measured. The results confirm that La^{-} is a very promising negative ion for laser-cooling applications.

Single-photon multiple detachment in fullerene negative ions: absolute ionization cross sections and the role of the extra electron.

We have obtained experimental photo-double- and photo-triple-detachment cross sections for the fullerene negative ion using Advanced Light Source photons of 17-90 eV. The cross sections are 2 and 2.5 times larger than those for C60 and appear to be compressed and shifted in photon energy as compared to C60. Our analysis reveals that the additional electron in C60- primarily produces screening which is responsible for the modification of the spectrum. Both screening effects, the shift and the compression, can be quantitatively accounted for by a linear transformation of the energy axis. Applying the transformation allows us to map the neutral and negative ion cross sections onto each other, pointing out the close relationship of correlated few-electron dynamics in neutral and negatively charged extended systems. In contrast, dynamics of neutral and negatively charged atoms or small molecules are typically not closely related.

Threshold photodetachment in a repulsive potential.

We report on the first experimental observation of a new threshold behavior observed in the 5(2)G partial channel in photodetachment of K(-). It arises from the repulsive polarization interaction between the detached electron and the residual K(5(2)G) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5(2)G) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.

Above threshold dissociation of vibrationally cold HD+ molecules.

The experimental study of molecular dissociation of H2+ by intense laser pulses is complicated by the fact that the ions are initially produced in a wide range of vibrational states, each of which responds differently to the laser field. An electrostatic storage device has been used to radiatively cool HD+ ions enabling the observation of above threshold dissociation from the ground vibrational state by 40 fs laser pulses at 800 nm. At the highest intensities used, dissociation through the absorption of at least four photons is found to be the dominant process.

Inner-shell photodetachment thresholds: unexpected long-range validity of the Wigner law.

Threshold behavior in inner-shell photodetachment is studied for the first time, specifically with 2-, 3-, or 4-electron emission from He- and S-. The threshold shapes are surprisingly consistent with the Wigner threshold law in all cases, despite large PCI effects observed in He-. In S-, the s-wave law is observed to agree with the data over an unprecedented range, more than an order of magnitude greater than predictions, and allows for the observation of the d-wave component. The measurements also demonstrate a means for obtaining precise core-excitation energies of free atoms.

The surgeon's responsibility for asepsis.

Eighty percent of postoperative wound infections result from bacteria acquired elsewhere than in the operating room. Concomitant infections--such as dermatitis; periodontitis; infections of the respiratory, gastrointestinal, or urinary tracts--are not identified preoperatively, despite a threat to the patient greater than that of anesthesia and surgery combined. Isolation of overt infection is neglected. The entire hospital becomes a reservoir of bacterial debris that is reflected in the carriage of pathogens by personnel and patients. Infections are often initiated by medical devices that invade the vascular system, respiratory tract, or urinary bladder. Professional leadership at the bedside is the key to detecting and correcting breaches in technique and setting an example of a philosophy of total patient care.

Detection of endotoxin on sterile catheters used for cardiac catheterization.

Pyrogen reactions during cardiac catheterization are an alarming complication that frightens patients and baffles many physicans. This report describes a simple, reproducible, precise technique for the measurement of endotoxin-like activity on the inner and outer surfaces of catheters intended for intravascular insertion. This technique is useful in documenting the cause of patient reactions. Quality control procedures should be instituted following the manufacture of angiographic catheters so that pyrogen-free products are availabe for patient use. Catheters processed in a hospital are easily contaminated with fever-producing lipopolysaccharides from tap water or from bacterial growth in residual moisture. Sterilization by steam or ethylene oxide does not destroy these lipopolysaccharides. Consequently, reprocessing reusable catheters must include concern for removing lipopolysaccharides as well as sterilization.

Ureaplasma urealyticum and Mycoplasma hominis in women with systemic lupus erythematosus.

OBJECTIVE: To determine the prevalence of genitourinary mycoplasma infection in women with systemic lupus erythematosus (SLE). METHODS: Urine specimens from 49 patients with SLE and 22 patients with chronic fatigue syndrome (CFS) were cultured for mycoplasma. Patient records were reviewed for medical history and SLE disease activity. RESULTS: Sixty-three percent of the SLE patients were culture positive, compared with 4.5% of the CFS patients (P less than 0.001). Neither corticosteroid treatment, SLE activity, nor age accounted for this difference. CONCLUSION: Genitourinary mycoplasma colonization occurs significantly more frequently in SLE than in CFS.