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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/6
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Publication Open Access HIPPIE: a new platform for ambient-pressure X-ray photoelectron spectroscopy at the MAX IV Laboratory(International Union of Crystallography (IUCr), 2021) Zhu, Suyun; Scardamaglia, Mattia; Kundsen, Jan; Sankari, Rami; Tarawneh, Hamed; Temperton, Robert; Pickworth, Louisa; Cavalca, Filippo; Wang, Chunlei; Tissot, Heloise; Weissenrieder, Jonas; Hagman, Benjamin; Gustafson, Johan; Lindgren, Fredrik; Kallquist, Ida; Maibach, Julia; Hahlin, Maria; Boix, Virginia; Gallo, Tamires; Rehman, Foqia; D'Acunto, Giulio; Schnadt, Joachim; Shavorskiy, Andrey; Department of Chemistry; Kaya, Sarp; Faculty Member; Department of Chemistry; College of Sciences; 116541HIPPIE is a soft X-ray beamline on the 3 GeV electron storage ring of the MAX IV Laboratory, equipped with a novel ambient-pressure X-ray photoelectron spectroscopy (APXPS) instrument. The endstation is dedicated to performing in situ and operando X-ray photoelectron spectroscopy experiments in the presence of a controlled gaseous atmosphere at pressures up to 30 mbar [1 mbar = 100 Pa] as well as under ultra-high-vacuum conditions. The photon energy range is 250 to 2200 eV in planar polarization and with photon fluxes >10(12) photons s(-1) (500 mA ring current) at a resolving power of greater than 10000 and up to a maximum of 32000. The endstation currently provides two sample environments: a catalysis cell and an electrochemical/liquid cell. The former allows APXPS measurements of solid samples in the presence of a gaseous atmosphere (with a mixture of up to eight gases and a vapour of a liquid) and simultaneous analysis of the inlet/outlet gas composition by online mass spectrometry. The latter is a more versatile setup primarily designed for APXPS at the solid-liquid (dip-and-pull setup) or liquid-gas (liquid microjet) interfaces under full electrochemical control, and it can also be used as an open port for ad hoc-designed non-standard APXPS experiments with different sample environments. The catalysis cell can be further equipped with an IR reflection-absorption spectrometer, allowing for simultaneous APXPS and IR spectroscopy of the samples. The endstation is set up to easily accommodate further sample environments.Publication Open Access Rotational-state-changing collisions between N-2(+) and Rb at low energies(American Physical Society (APS), 2020) Doerfler, A. D.; Villarreal, P.; Gonzalez-Lezana, T.; Gianturco, F. A.; Willitsch, S.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129We present a theoretical study of rotationally elastic and inelastic collisions between molecular nitrogen ions and Rb atoms in the sub-Kelvin temperature regime prevalent in ion-atom hybrid trapping experiments. The cross sections for rotational excitation and de-excitation collisions were calculated using quantum-scattering methods on ab initio potential energy surfaces for the energetically lowest singlet electronic channel of the system. We find that the rotationally inelastic collision rates are at least an order of magnitude smaller than the charge-exchange rates found in this system, rendering inelastic processes a minor channel under the conditions of typical hybrid trapping experiments.Publication Open Access Chaotic behavior of triatomic clusters(American Physical Society (APS), 1997) Elmacı, N.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The dynamics of triatomic clusters is investigated employing two-body Lennard-Jones and three-body Axilrod-Teller potential functions. Lyapunov exponents are calculated for the total energy range of -2.70 epsilon <E< -0.72 epsilon. The effects of the initial geometry of the cluster, its angular momentum, and the magnitude of three-body interactions are analyzed. It has been found that the dominating factor for the extent of chaotic behavior is the energy assigned to vibrational modes. The introduction of the rotational motion regularizes the dynamics in spite of a higher degree of nonlinearity. The three-body terms in the potential function affect the extent of the chaos in different manners depending on the initial geometry of the cluster. Finally, the time evolution of heterogeneous clusters generated by varying the size, mass, and the interaction strength of a single atom is observed. Their Lyapunov exponent spectra show that the additional nonlinearity reduces the chaotic behavior of the system in most of the cases.Publication Open Access Vibrational quenching at ultralow energies: calculations of the Li-2((1)Sigma(+)(g);nu >> 0)+He superelastic scattering cross sections(American Physical Society (APS), 2006) Bodo, Enrico; Gianturco, Franco A.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Accurate quantum calculations have been carried out at ultralow energies (from 10(-2) to 10(-6) cm(-1)) for the vibrational deexcitation of Li-2((1)Sigma(+)(g)) by collisions with He, starting from a broad range of initial highly excited vibrational levels. The results indicate the clear dominance of a few transitions with the smallest Delta nu changes and show the overall deexcitation cross sections to markedly depend on the initial vibrational state of the molecule, in line with earlier results on H-2+He [Balakrishan Phys. Rev. Lett. 80, 3224 (1998)] vibrational quenching. A connection is made with very recent measurements on the vibrational quenching of ultracold Cs-2 molecules in optical traps that were instead found to behave in a very different manner. Numerical experiments on the present system as well as on the H-3 reaction strongly suggest a possible explanation for such differences.Publication Open Access Crystallization of ion clouds in octupole traps: structural transitions, core melting, and scaling laws(American Physical Society (APS), 2009) Calvo, F.; Champenois, C.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The stable structures and melting properties of ion clouds in isotropic octupole traps are investigated using a combination of semianalytical and numerical models, with a particular emphasis at finite-size scaling effects. Small-size clouds are found to be hollow and arranged in shells corresponding approximately to the solutions of the Thomson problem. The shell structure is lost in clusters containing more than a few thousands of ions, the inner parts of the cloud becoming soft and amorphous. While melting is triggered in the core shells, the melting temperature follows the rule expected for three-dimensional dense particles, with a depression scaling linearly with the inverse radius.Publication Open Access Targeting of epidermal growth factor receptor (EGFR)-positive pancreatic cancer cell lines with cetuximab-conjugated near-infrared silver sulphide quantum dots(Society of Photo-optical Instrumentation Engineers (SPIE), 2019) Labib, Peter L.; Yaghini, Elnaz; Davidson, Brian R.; MacRobert, Alexander J.; Loizidou, Marilena; Pereira, Stephen P.; N/A; Department of Chemistry; Hashemkhani, Mahshid; Acar, Havva Funda Yağcı; PhD Student; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 178902Introduction: fluorescence-guided surgery could potentially reduce local recurrence after pancreatic cancer resection. However, the ideal contrast agent for this purpose is not yet determined. The monoclonal antibody cetuximab targets the EGFR receptor, which is overexpressed in 64% of pancreatic cancers. We investigated the efficacy of near-infrared emitting silver sulphide Quantum Dot (QD)-cetuximab nanoconjugates for targeting EGFR-positive pancreatic cancer. Methods: 2-Mercaptopropionic acid-coated QDs were prepared from AgNO3 and Na2S. Pancreatic cancer cell lines PANC-1 and CFPAC-1 were confirmed EGFR-positive using a commercial AlexaFluor488-cetuximab probe. Nonconjugated QD and cetuximab-conjugated QD (QD-cetuximab) toxicity was assessed after 24 and 48 hours using MTT assay. Fluorescence microscopy was performed following a) formaldehyde-fixed immunofluorescence and b) live staining with QD-cetuximab for four hours at concentrations corresponding to 0, 10, 50, 100, 200, 400 and 600μg ml-1 of silver. Results: untargeted QDs were non-toxic in both cell lines after 48 hours at all investigated concentrations, whereas QDcetuximab was toxic at 100μg ml-1 after 24 hours in PANC-1 and at 10μg ml-1 in CFPAC-1. Fixed immunofluorescence demonstrated EGFR targeting by QD-cetuximab at concentrations of 50μg ml-1 upwards in both cell lines. Live staining demonstrated similar efficacy of EGFR targeting up to 50μg ml-1, although a reduction of fluorescence at higher concentrations was observed when compared to fixed immunofluorescence. Conclusion: silver sulphide QD-cetuximab nanoconjugates have the potential to target live EGFR-positive pancreatic cancer cells at doses of up to 50 μg ml-1. The reduction in QD fluorescence observed at higher concentrations is likely to be secondary to cetuximab toxicity.Publication Open Access Angular-momentum-driven chaos in small clusters(American Physical Society (APS), 1998) Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129The effects of the rotational motion on the chaotic behavior of triatomic Lennard-Jones clusters are studied. A set of initial momentum distributions with tunable parameters is chosen to correspond to various rigid-body rotations around symmetry axes of the cluster. By smoothly varying the direction of the initial kicks given to the cluster, periodic transitions between regular and chaotic regimes are obtained. A study of initial conditions leading up to such transitions shows that the major factor that determines the extent of the chaotic behavior is the initial partitioning of the kinetic energy between the rotational and vibrational motion. From the analysis of the time evolution of various properties it is concluded that the basic role of this initial partitioning is to control the energy transfer between the kinetic and the potential energy.Publication Open Access Quenching of internal rotations versus collisional cooling at ultralow energies for weakly interacting partners: Cs-2((3)Sigma(+)(u)) with He-3,He-4(American Physical Society (APS), 2010) Caruso, D.; Tacconi, M.; Gianturco, F. A.; Department of Chemistry; Yurtsever, İsmail Ersin; Faculty Member; Department of Chemistry; College of Sciences; 7129Quantum-scattering calculations at ultralow (close to 10(-6) cm(-1)) collision energies are carried out for the Cs dimer in its spin-stretched triplet state, interacting with helium. An ab initio potential energy surface is computed and employed, while the target molecule is kept in its ground vibrational state and several excitated initial rotational states are considered in the quantum dynamics. The highly anisotropic interaction is seen to cause, in spite of its weakness, internal energy quenching rates comparable with the efficiency of the collisional cooling of relative kinetic energies. The rates of spin-flip processes are also analyzed and compared with pure rotational quenching events.Publication Open Access Structure and dynamics of ion clusters in linear octupole traps: phase diagrams, chirality, and melting mechanisms(American Physical Society (APS), 2011) Calvo, F.; Department of Chemistry; Yurtsever, İsmail Ersin; Önal, Emre Doruk; Faculty Member; Department of Chemistry; College of Sciences; 7129; N/AThe stable structures and melting dynamics of clusters of identical ions bound by linear octupole radiofrequency traps are theoretically investigated by global optimization methods and molecular dynamics simulations. By varying the cluster sizes in the range of 10-1000 ions and the extent of trap anisotropy by more than one order of magnitude, we find a broad variety of stable structures based on multiple rings at small sizes evolving into tubular geometries at large sizes. The binding energy of these clusters is well represented by two contributions arising from isotropic linear and octupolar traps. The structures generally exhibit strong size effects, and chiral arrangements spontaneously emerge in many crystals. Sufficiently large clusters form nested, coaxial tubes with different thermal stabilities. As in isotropic octupolar clusters, the inner tubes melt at temperatures that are lower than the overall melting point.Publication Open Access Single glycerol/water microdroplets standing on a superhydrophobic surface: optical microcavities promising original applications(Society of Photo-optical Instrumentation Engineers (SPIE), 2007) Department of Physics; Department of Chemistry; Kiraz, Alper; Dündar, Mehmet Ali; Demirel, Adem Levent; Doğanay, Sultan; Kurt, Adnan; Sennaroğlu, Alphan; Yüce, Mehdi Yavuz; Faculty Member; Faculty Member; Undergraduate Student; Teaching Faculty; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; 22542; N/A; 6568; N/A; 194455; 23851; N/AGlycerol/water microdroplets take almost spherical shapes when standing on a superhydrophobic surface. Hence they are suitable to function as optical microcavities. Using Rhodamine B doped water microdroplets, large spectral tunability of the whispering gallery modes (WGMs) (>5 nm) was observed. Tunability was achieved by evaporation/condensation in a current controlled mini humidity chamber. Experiments revealed a mechanism stabilizing the volume of these microdroplets with femtoliter resolution. The mechanism relied on the interplay between the condensation rate that was kept constant and the size dependent laser induced heating. The radii of individual water microdroplets (>5 mu m) stayed within a few nanometers during long time periods (several minutes). By blocking the laser excitation for 500 msec, the stable volume of individual microdroplets were changed stepwise. Laser emission was also observed from Rhodamine B doped glycerol/water microdroplets using a pulsed, frequency-doubled Nd:YAG laser (lambda=532 nm) as the excitation source. The observed largely tunable WGMs and laser emission can pave way for novel applications in optical communication systems. Besides due to the sensitivity of the WGMs to the size and shape of the microdroplets, the results can find applications in characterizing superhydrophobic surfaces and investigating liquid-solid surfaces.