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  • 1
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    Terminal coordination of diatomic boron monofluoride to iron (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉Boron monofluoride (BF) is a diatomic molecule with 10 valence electrons, isoelectronic to carbon monoxide (CO). Unlike CO, which is a stable molecule at room temperature and readily serves as both a bridging and terminal ligand to transition metals, BF is unstable below 1800°C in the gas phase, and its coordination chemistry is substantially limited. Here, we report the isolation of the iron complex Fe(BF)(CO)〈sub〉2〈/sub〉(CNAr〈sup〉Tripp2〈/sup〉)〈sub〉2〈/sub〉 [Ar〈sup〉Tripp2〈/sup〉, 2,6-(2,4,6-(〈i〉i-〈/i〉Pr)〈sub〉3〈/sub〉C〈sub〉6〈/sub〉H〈sub〉2〈/sub〉]〈sub〉2〈/sub〉C〈sub〉6〈/sub〉H〈sub〉3〈/sub〉; 〈i〉i〈/i〉-Pr, 〈i〉iso〈/i〉-propyl], featuring a terminal BF ligand. Single-crystal x-ray diffraction as well as nuclear magnetic resonance, infrared, and Mössbauer spectroscopic studies on Fe(BF)(CO)〈sub〉2〈/sub〉(CNAr〈sup〉Tripp2〈/sup〉)〈sub〉2〈/sub〉 and the isoelectronic dinitrogen (N〈sub〉2〈/sub〉) and CO complexes Fe(N〈sub〉2〈/sub〉)(CO)〈sub〉2〈/sub〉(CNAr〈sup〉Tripp2〈/sup〉)〈sub〉2〈/sub〉 and Fe(CO)〈sub〉3〈/sub〉(CNAr〈sup〉Tripp2〈/sup〉)〈sub〉2〈/sub〉 demonstrate that the terminal BF ligand possesses particularly strong -donor and -acceptor properties. Density functional theory and electron-density topology calculations support this conclusion.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Evaluation of the effects of a plasma activated medium on cancer cells (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-17
    Description: The interaction of low temperature plasma with liquids is a relevant topic of study to the field of plasma medicine. This is because cells and tissues are normally surrounded or covered by biological fluids. Therefore, the chemistry induced by the plasma in the aqueous state becomes crucial and usually dictates the biological outcomes. This process became even more important after the discovery that plasma activated media can be useful in killing various cancer cell lines. Here, we report on the measurements of concentrations of hydrogen peroxide, a species known to have strong biological effects, produced by application of plasma to a minimum essential culture medium. The activated medium is then used to treat SCaBER cancer cells. Results indicate that the plasma activated medium can kill the cancer cells in a dose dependent manner, retain its killing effect for several hours, and is as effective as apoptosis inducing drugs.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 3
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    Detection and characterization of singly deuterated silylene, SiHD, via optical spectroscopy (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-06-28
    Description: Singly deuterated silylene has been detected and characterized in the gas-phase using high-resolution, two-dimensional, optical spectroscopy. Rotationally resolved lines in the 0 0 0 X ̃ 1 A ′ → A ̃ 1 A ″ band are assigned to both c -type perpendicular transition and additional parallel, axis-switching induced bands. The extracted rotational constants were combined with those for SiH 2 and SiD 2 to determine an improved equilibrium bond length, r SiH , and bond angle, θ, of 1.5137 ± 0.0003 Å and 92.04° ± 0.05°, and 1.4853 ± 0.0005 Å and 122.48° ± 0.08° for the X ̃ 1 A ′ 0 , 0 , 0 and A ̃ 1 A ″ ( 0 , 0 , 0 ) state respectively. The dispersed fluorescence consists of a long progression in the A ̃ 1 A ″ ( 0 , 0 , 0 ) → X ̃ 1 A ′ ( 0 , ν 2 , 0 ) emission which was analyzed to produce vibrational parameters. A strong quantum level dependence of the rotationally resolved radiative decay curves is analyzed.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 4
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    The near-infrared spectrum of ethynyl radical (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-08-18
    Description: Transient diode laser absorption spectroscopy has been used to measure three strong vibronic bands in the near infrared spectrum of the C 2 H, ethynyl, radical not previously observed in the gas phase. The radical was produced by ultraviolet excimer laser photolysis of either acetylene or (1,1,1)-trifluoropropyne in a slowly flowing sample of the precursor diluted in inert gas, and the spectral resolution was Doppler-limited. The character of the upper states was determined from the rotational and fine structure in the observed spectra and assigned by measurement of ground state rotational combination differences. The upper states include a 2 Σ + state at 6696 cm −1 , a second 2 Σ + state at 7088 cm −1 , and a 2 Π state at 7110 cm −1 . By comparison with published calculations [R. Tarroni and S. Carter, J. Chem. Phys 119 , 12878 (2003); Mol. Phys. 102 , 2167 (2004)], the vibronic character of these levels was also assigned. The observed states contain both X 2 Σ + and A 2 Π electronic characters. Several local rotational level perturbations were observed in the excited states. Kinetic measurements of the time-evolution of the ground state populations following collisional relaxation and reactive loss of the radicals formed in a hot, non-thermal, population distribution were made using some of the strong rotational lines observed. The case of C 2 H may be a good place to investigate the behavior at intermediate pressures of inert colliders, where the competition between relaxation and reaction can be tuned and observed to compare with master equation models, rather than deliberately suppressed to measure thermal rate constants.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 5
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    First results from the Cornell high Q cw full linac cryo- module (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-12-19
    Description: Cornell University has finished building a 10 m long superconducting accelerator module as a prototype of the main linac of a proposed ERL facility. This module houses 6 superconducting cavities- operated at 1.8 K in continuous wave (CW) mode - with individual HOM absorbers and one magnet/ BPM section. In pushing the limits, a high quality factor of the cavities (2•10 10 ) and high beam currents (100 mA accelerated plus 100 mA decelerated) were targeted. The design of the cryomodule and the results of components tested before assembly will be presented in this paper.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 6
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    Further investigation of g factors for the lead monofluoride ground state (2015)
    American Physical Society (APS)
    Details
    Publication Date: 2015-09-17
    Description: Author(s): L. V. Skripnikov, A. N. Petrov, A. V. Titov, R. J. Mawhorter, A. L. Baum, T. J. Sears, and J.-U. Grabow We report the results of our theoretical study and analysis of earlier experimental data for the g -factor tensor components of the ground 2 Π 1 / 2 state of the free PbF radical. The values were obtained both within the relativistic coupled-cluster method combined with the generalized relativistic effec… [Phys. Rev. A 92, 032508] Published Tue Sep 15, 2015
    Keywords: Atomic and molecular structure and dynamics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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  • 7
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    Nitrogen-doped 9-cell cavity performance in a test cryomodule for LCLS-IIa) (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-01-14
    Description: The superconducting RF linac for Linac Coherent Light Source-II calls for 1.3 GHz 9-cell cavities with an average intrinsic quality factor Q 0 of 2.7 × 10 10 at 2.0 K and 16 MV/m accelerating gradient. Two niobium 9 cell cavities, prepared with nitrogen-doping at Fermilab, were assembled into the Cornell Horizontal Test Cryomodule (HTC) to test cavity performance in a cryomodule that is very similar to a full LCLS-II cryomodule. The cavities met LCLS-II specifications with an average quench field of 17 MV/m and an average Q 0 of 3 × 10 10 . The sensitivity of the cavities' residual resistance to ambient magnetic field was determined to be 0.5 nΩ/mG during fast cool down. In two cool downs, a heater attached to one of the cavity beam tubes was used to induce large horizontal temperature gradients. Here, we report on the results of these first tests of nitrogen-doped cavities in a cryomodule, which provide critical information for the LCLS-II project.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 8
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    Thermocurrents and their role in high Q cavity performance (2016)
    American Physical Society (APS)
    Details
    Publication Date: 2016-02-13
    Description: Author(s): R. Eichhorn, C. Daly, F. Furuta, A. Ganshyn, M. Ge, D. Gonnella, D. Hall, V. Ho, G. H. Hoffstaetter, M. Liepe, J. May-Mann, T. O’Connell, S. Posen, P. Quigley, J. Sears, and V. Veshcherevich Over the past years it became evident that the quality factor of a superconducting cavity is not only determined by its surface preparation procedure, but is also influenced by the way the cavity is cooled down. Moreover, different data sets exist, some of which indicate that a slow cooldown through… [Phys. Rev. Accel. Beams 19, 012001] Published Tue Jan 19, 2016
    Keywords: Radio Frequency Calculations and Technology
    Electronic ISSN: 1098-4402
    Topics: Physics
    Published by American Physical Society (APS)
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  • 9
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    Quadrupole splittings in the near-infrared spectrum of 14NH3 (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-10-14
    Description: Sub-Doppler, saturation dip, spectra of lines in the v 1 + v 3 , v 1 + 2 v 4 , and v 3 + 2 v 4 bands of 14 NH 3 have been measured by frequency comb-referenced diode laser absorption spectroscopy. The observed spectral line widths are dominated by transit time broadening and show resolved or partially-resolved hyperfine splittings that are primarily determined by the 14 N quadrupole coupling. Modeling of the observed line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the excited state level has hyperfine splittings similar to the same rotational level in the ground state. The data provide accurate frequencies for the line positions and easily separate lines overlapped in Doppler-limited spectra. The observed hyperfine splittings can be used to make and confirm rotational assignments and ground state combination differences obtained from the measured frequencies are comparable in accuracy to those obtained from conventional microwave spectroscopy. Several of the measured transitions do not show the quadrupole hyperfine splittings expected based on their existing rotational assignments. Either the assignments are incorrect or the upper levels involved are perturbed in a way that affects the nuclear hyperfine structure.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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  • 10
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    Photo-assisted intersystem crossing: The predominant triplet formation mechanism in some isolated polycyclic aromatic molecules excited with pulsed lasers (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-07-25
    Description: Naphthalene, anthracene, and phenanthrene are shown to have very long-lived triplet lifetimes when the isolated molecules are excited with nanosecond pulsed lasers resonant with the lowest singlet state. For naphthalene, triplet state populations are created only during the laser pulse, excluding the possibility of normal intersystem crossing at the one photon level, and all molecules have triplet lifetimes greater than hundreds of microseconds, similar to the behavior previously reported for phenylacetylene. Although containing 7–12 thousand cm −1 of vibrational energy, the triplet molecules have ionization thresholds appropriate to vibrationless T 1 states. The laser power dependences (slopes of log-log power plots) of the excited singlet and triplet populations are about 0.7 for naphthalene and about 0.5 for anthracene. Kinetic modeling of the power dependences successfully reproduces the experimental results and suggests that the triplet formation mechanism involves an enhanced spin orbit coupling caused by sigma character in states at the 2-photon level. Symmetry adapted cluster-configuration interaction calculations produced excited state absorption spectra to provide guidance for estimating kinetic rates and the sigma character present in higher electronic states. It is concluded that higher excited state populations are significant when larger molecules are excited with pulsed lasers and need to be taken into account whenever discussing the molecular photodynamics.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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