107 research outputs found
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Towards Measuring the Electron Electric Dipole Moment Using Trapped Molecular Ions
Permanent electric dipole moments have been the subject of experimental investigation for the past sixty years, as they entail the breaking of fundamental symmetries and provide a sensitive probe for physics beyond the Standard Model. This thesis describes an experiment aimed at measuring the electron electric dipole moment (eEDM) using trapped molecular ions. The 3Î1 level of certain diatomic ions are desirable in eEDM searches due to their high polarizability, large eEDM enhancement factor, and relative insensitivity to magnetic fields. Ions allow for simple trapping and long interrogation times, but require a time-varying electric bias field in order to probe the eEDM.
I will discuss the criteria for molecular ions in our experiment and our current candidates. A laser-ablation supersonic-expansion beam source has been developed to create and cool molecular ions. These ions have been loaded into a linear rf Paul trap and alternative photoionization methods for state-selective ion creation have been tested. Various experimental methods for performing the necessary spin resonance measurement are discussed. Sources of both decoherence and systematic errors have been identified and estimated. The experiment described in this thesis should be capable of a factor of 30 improvement on the current limit of the eEDM
Nanoparticle growth following photochemical αâ and ÎČâpinene oxidation at Appledore Island during International Consortium for Research on Transport and Transformation/Chemistry of Halogens at the Isles of Shoals 2004
Nanoparticle events were observed 48 times in particle size distributions at Appledore Island during the International Consortium for Atmospheric Research on Transport and Transformation/Chemistry of Halogens on the Isles of Shoals (ICARTT/CHAiOS) field campaign from 2 July to 12 August of 2004. Eighteen of the nanoparticle events showed particle growth and occurred during mornings when peaks in mixing ratios of αâ and ÎČâpinene and ozone made production of condensable products from photochemical oxidation probable. Many pollutants and other potential precursors for aerosol formation were also at elevated mixing ratios during these events, including NO, HNO3, NH3, HCl, propane, and several other volatile organic carbon compounds. There were no consistent changes in particle composition, although both submicron and supermicron particles included high maximum concentrations of methane sulfonate, sulfate, iodide, nitrate, and ammonium during these events. Nanoparticle growth continued over several hours with a nearly linear rate of increase of diameter with time. The observed nanoparticle growth rates varied from 3 to 13 nm hâ1. Apparent nanoparticle aerosol mass fractions (yields) were estimated to range from less than 0.0005 to almost 1 using αâ and ÎČâpinene as the presumed particle source. These apparent high aerosol mass fractions (yields) at low changes in aerosol mass are up to two orders of magnitude greater than predictions from extrapolated laboratory parameterizations and may provide a more accurate assessment of secondary organic aerosol formation for estimating the growth of nanoparticles in global models
REMPI Spectroscopy of HfF
The spectrum of electronic states at 30000--33000 cm in hafnium
fluoride has been studied using (1+1) resonance-enhanced multi-photon
ionization (REMPI) and (1+1) REMPI. Six and ten
vibronic bands have been characterized. We report the molecular constants for
these bands and estimate the electronic energies of the excited states using a
correction derived from the observed isotope shifts. When either of two closely
spaced electronic states is used as an intermediate state to access
autoionizing Rydberg levels, qualitatively distinct autoionization spectra are
observed. The intermediate state-specificity of the autoionization spectra
bodes well for the possibility of using a selected state as an
intermediate state to create ionic HfF in various selected quantum states,
an important requirement for our electron electric dipole moment (eEDM) search
in HfF.Comment: 11 pages, 8 figures, 1 tabl
Near-Infrared LIF Spectroscopy of HfF
The molecular ion HfFâș is the chosen species for a JILA experiment to measure the electron electric dipole moment (eEDM). Detailed knowledge of the spectrum of HfF is crucial to prepare HfFâș in a state suitable for performing an eEDM measurement [1]. We investigated the near-infrared electronic spectrum of HfF using laser-induced fluorescence (LIF) of a supersonic molecular beam. We discovered eight unreported bands, and assign each of them unambiguously, four to vibrational bands belonging to the transition [13.8]0.5 ← X1.5, and four to vibrational bands belonging to the transition [14.2]1.5 ← X1.5. Additionally, we report an improved measurement of vibrational spacing of the ground state, as well as anharmonicity ωâxâ.</p
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High-Resolution Spectroscopy on Trapped Molecular Ions in Rotating Electric Fields: A New Approach for Measuring the Electron Electric Dipole Moment
High-resolution molecular spectroscopy is a sensitive probe for violations of fundamental symmetries. Symmetry violation searches often require, or are enhanced by, the application of an electric field to the system under investigation. This typically precludes the study of molecular ions due to their inherent acceleration under these conditions. Circumventing this problem would be of great benefit to the high-resolution molecular spectroscopy community since ions allow for simple trapping and long interrogation times, two desirable qualities for precision measurements. Our proposed solution is to apply an electric field that rotates at radio frequencies. We discuss considerations for experimental design as well as challenges in performing precision spectroscopic measurements in rapidly time-varying electric fields. Ongoing molecular spectroscopy work that could benefit from our approach is summarized. In particular, we detail how spectroscopy on a trapped diatomic molecular ion with a ground or metastable ³Δâ level could prove to be a sensitive probe for a permanent electron electric dipole moment (eEDM).</p
Measuring the Loschmidt amplitude for finite-energy properties of the Fermi-Hubbard model on an ion-trap quantum computer
Calculating the equilibrium properties of condensed matter systems is one of
the promising applications of near-term quantum computing. Recently, hybrid
quantum-classical time-series algorithms have been proposed to efficiently
extract these properties from a measurement of the Loschmidt amplitude from initial states and a
time evolution under the Hamiltonian up to short times . In this
work, we study the operation of this algorithm on a present-day quantum
computer. Specifically, we measure the Loschmidt amplitude for the
Fermi-Hubbard model on a -site ladder geometry (32 orbitals) on the
Quantinuum H2-1 trapped-ion device. We assess the effect of noise on the
Loschmidt amplitude and implement algorithm-specific error mitigation
techniques. By using a thus-motivated error model, we numerically analyze the
influence of noise on the full operation of the quantum-classical algorithm by
measuring expectation values of local observables at finite energies. Finally,
we estimate the resources needed for scaling up the algorithm.Comment: 18 pages, 12 figure
Priming with recombinant auxotrophic BCG expressing HIV-1 Gag, RT and Gp120 and boosting with recombinant MVA induces a robust T cell response in mice
In previous studies we have shown that a pantothenate auxotroph of Myocbacterium bovis BCG (BCGΠpanCD ) expressing HIV-1 subtype C Gag induced Gag-specific immune responses in mice and Chacma baboons after prime-boost immunization in combination with matched rMVA and VLP vaccines respectively. In this study recombinant BCG (rBCG) expressing HIV-1 subtype C reverse transcriptase and a truncated envelope were constructed using both the wild type BCG Pasteur strain as a vector and the pantothenate auxotroph. Mice were primed with rBCG expressing Gag and RT and boosted with a recombinant MVA, expressing a polyprotein of Gag, RT, Tat and Nef (SAAVI MVA-C). Priming with rBCGΠpanCD expressing Gag or RT rather than the wild type rBCG expressing Gag or RT resulted in higher frequencies of total HIV-specific CD8 + T cells and increased numbers of T cells specific to the subdominant Gag and RT epitopes. Increasing the dose of rBCG from 10 5 cfu to 10 7 cfu also led to an increase in the frequency of responses to subdominant HIV epitopes. A mix of the individual rBCGΠpanCD vaccines expressing either Gag, RT or the truncated Env primed the immune system for a boost with SAAVI MVA-C and generated five-fold higher numbers of HIV-specific IFN-γ-spot forming cells than mice primed with rBCGΠpanCD containing an empty vector control. Priming with the individual rBCGΠpanCD vaccines or the mix and boosting with SAAVI MVA-C also resulted in the generation of HIV-specific CD4 + and CD8 + T cells producing IFN-γ and TNF-α and CD4 + cells producing IL-2. The rBCG vaccines tested in this study were able to prime the immune system for a boost with rMVA expressing matching antigens, inducing robust, HIV-specific T cell responses to both dominant and subdominant epitopes in the individual proteins when used as individual vaccines or in a mix
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