Welcome to the Boutis NMR group @ York College of CUNY

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The Graduate Center of CUNY








Advanced Electricity and Magnetism(Phys 321) Fall 2008 Chemistry 86905 Magnetic Resonance Spectroscopy Spring 2007 Our NMR Group

Yisa Rumala Gregory S. Boutis
Assistant Professor of Physics
Office: 2F09C
Office Phone: (718)262-2889
Lab phone (718)262-2417
email: gboutis@york.cuny.edu

B.A. Physics, Cornell University
Ph.D. Nuclear Science and Engineering, Massachusetts Institute of Technology

Postdoctoral research at the University of Hawaii at Manoa, Department of Chemistry focusing on NMR of elastin and in Magnetic Resonance Force Microscopy (MRFM) at the Johns Hopkins University Applied Physics Laboratory.

RESEARCH INTERESTS:
Solid State NMR
NMR imaging
NMR Hardware development

SELECTED PUBLICATIONS:



  • R. Roopchand, E. S. Mananga and G.S. Boutis* 'Method for suppressing finite pulse width artifacts of spin I=1 composite pulse based quadrupolar echo spectroscopy' submitted to the Journal of Magnetic Resonance.

  • E.S. Mananga, C. D. Hsu, S. Ishmael, T. Islam and G. S. Boutis*, 'Probing the validity of average Hamiltonian theory for spin I=1, 3/2 and 5/3 nuclei by analyzing a simple two pulse sequence' Journal of Magnetic Resonance 193, 10 – 22, 2008. [PDF]

    In this work, we investigate the accuracy of controlling spin I=1, 3/2 and 5/2 spin systems by average Hamiltonian theory. By way of example, we consider a simple two-pulse echo sequence and compare this perturbation scheme to a numerical solution of the Von Neumann equation. For the different values of I, we examine this precision as a function of the quadrupolar coupling as well as various experimental parameters such as the pulse spacing and pulse width. Experiments and simulations on I=3/2 and I=5/2 spin systems are presented that highlight a spectral artifact introduced due to finite pulse widths, as predicted by average Hamiltonian theory. The control of these spin systems by this perturbation scheme is considered by investigating a phase cycling scheme that suppresses these artifacts to zeroth order of the Magnus expansion.



  • G.S. Boutis*, C. Renner, T. Isahkarov, T. Islam, L. Kannangara, P. Kauer, E. Mananga, A. Ntekim, Y. S. Rumala, D. Wei 'High resolution q-space imaging studies of water in elastin' Biopolymers 87, 5-6, 352-359, 2007 [PDF].

    We report on the direct measurement of the molecular diffusion coefficients of water confined to purified bovine nuchal ligament elastin by high resolution q-space NMR imaging. The experimental data indicate that water trapped within an elastin fiber has two distinguishable molecular diffusion coefficients. The component with the slowest mobility has a diffusion coefficient on the order of 10-6 cm2/s that varies inversely with the diffusion time and is seen to reduce near 37C. The component with higher mobility has a diffusion coefficient reminiscent of free water but is observed to also behave similarly at 37C. From our experimental data we extract the surface to volume ratio of pores within elastin and associated changes as a function of temperature.



  • E. S. Mananga, R. Roopchand, Y. S. Rumala and G. S. Boutis*, 'On the application of magic echo cycles for quadrupolar echo spectroscopy of spin-1 nuclei' Journal of Magnetic Resonance, 185, 28, 2007 [PDF]

    Magic echo cycles are introduced for performing quadrupolar echo spectroscopy of spin-1 nuclei. An analysis is performed via average Hamiltonian theory showing that the evolution under chemical shift or static field inhomogeneity can be refocused simultaneously with the quadrupolar interaction using these cycles. Due to the higher convergence in the Magnus expansion, with sufficient RF power, magic echo based quadrupolar echo spectroscopy outperforms the conventional two pulse quadrupolar echo in signal to noise. Experiments highlighting a signal to noise enhancement over the entire bandwidth of the quadrupolar pattern of a powdered sample of deuterated polyethelene are shown.



  • E. S. Mananga, Y. S. Rumala and G. S. Boutis* 'Finite pulse width artifact suppression in spin-1 quadrupolar echo spectra by phase cycling' Journal of Magnetic Resonance, 181, 296-303, 2006 . [PDF]

    A phase cycling scheme for suppressing spectral artifacts introduced in quadrupolar echo spectroscopy of spin-1 nuclei due to finite pulse width effects is presented. The phase cycling scheme is developed using the formalism of average Hamiltonian theory and fictitious spin-1 operators. A simulation and experiment on deuterated polyethelene is performed highlighting the spectral artifact introduced by finite pulse widths and successful removal with the proposed phase cycling scheme.



  • G. S. Boutis, D. Greenbaum, H. J. Cho, C. Ramanathan, D.G. Cory. 'Spin Diffusion of two-spin correlated states in a dielectric crystal', Physical Review Letters 92, 13, 2003. [PDF]

    Reciprocal space measurements of spin diffusion in a single crystal of calcium fluoride (CaF2) have been extended to dipolar ordered states. The experimental results for the component of the spin diffusion rate parallel to the external field are D=29 ± 3 x 10-12 cm2/s for the [001] direction and D=33 ± 4 x 10-12 cm2/s for the [111] direction. The measured diffusion rates for dipolar order are faster than those for Zeeman order and are considerably faster than predicted by simple theoretical models. It is suggested that constructive interference in the transport of the two-spin states is responsible for this enhancement. As expected, the anisotropy in the diffusion rates is observed to be significantly less for dipolar order compared to the Zeeman case.



  • G. S. Boutis, P. Cappellaro, H. Cho, C. Ramanathan, D. G. Cory. 'Pulse error compensating symmetric magic echo trains' Journal of Magnetic Resonance 161, 132-137, 2003. [PDF]

    We present improved line-narrowing sequences for dipolar coupled spin systems, based on a train of magic-echoes which are compensated for the effects of finite pulse widths and utilize symmetry properties of supercycles. Sequences are introduced for spectroscopy and imaging by proper choice of a phase alternating scheme. Using a 16 pulse time-suspension magic-echo cycle, the highest level of line-narrowing achieved was 2.7 Hz for the [100] direction of a single crystal of calcium fluoride, a reduction in linewidth by 4 orders of magnitude.



  • C. Ramanathan, H. Cho, P. Cappellaro, G. S. Boutis and D. G. Cory. 'Exploring large nuclear spin systems in the solid state using NMR', Conference Proceedings of the 6th International Conference on Quantum Communication, Measurement and Computing. Ed. J. Shapiro and O. Hirota, Rinton Press, 2003.

    In the approach to designing and implementing a scalable quantum computer, it is essential that we develop the ability to accurately perform desired unitary transformations in a large Hilbert space, as well as understand the sensitivity to decoherence of states in this space. In this talk we describe the creation of spin states containing multiple quantum coherences using solid state nuclear magnetic resonance techniques, and show how the properties of these states can be inferred by encoding them in different basis representations. We also explore the sensitivity of these states to noise and decoherence. These multiple quantum coherences correspond to off-diagonal terms in the density matrix in the Zeeman basis, with higher order coherences located farther off the diagonal. The nuclear spins in a dielectric solid such as calcium fluoride have very long spin-lattice relaxation times, ranging from minutes to days depending on the concentration of paramagnetic impurities present in the crystal. It is therefore possible to investigate the dynamical behaviour of these spins under the action of their mutual dipolar couplings and applied radiofrequency perturbations, while they are essentially isolated from their environment. Average Hamiltonian Theory provides a framework within which we can design experiments in which the internal Hamiltonian of the spins is modulated by radiofrequency pulses so that the spins appear to evolve under a suitably designed effective Hamiltonian. This methodology has been used extensively in the design of NMR experiments. Such studies provide us with an experimental paradigm within which we can begin to understand the dynamics of spins in a large Hilbert space under the action of a many-body Hamiltonian.



  • C. Ramanathan, H. Cho. P. Cappellaro, G. S. Boutis and D. G. Cory. 'Encoding multiple quantum coherences in non-commuting bases' Chemical Physics Letters 369, 311-317, 2003. [PDF]

    Multiple quantum (MQ) coherences are characterized bytheir coherence number and the number of spins that make up the state, though onlythe coherence number is normallymeasured. We present a simple set of measurements that extend our knowledge of the MQ state byrecording the coherences in two non-commuting bases - the x and the z bases (related by a similarity transformation). The measurement of coherences in a basis other than the usual z basis also permits the studyof spin dynamics under Hamiltonians that conserve z basis coherence number.



  • D. G. Cory, R. Laflamme, E. Knill, L. Viola, T. F. Havel, N. Boulant, G.S. Boutis, E. Fortunato, S. Lloyd, R. Martinez, C. Negrevergne, M.Pravia, Y.Sharf, G. Teklemariam, Y. S. Weinstein and W. H. Zurek. 'NMR Based Quantum Information Processing: Achievements and Prospects', Fortschr. Phys. 48, 875-904, 2000. [PDF]

    Nuclear magnetic resonance (NMR) provides an experimental setting to explore physical implementa- tions of quantum information processing (QIP). Here we introduce the basic background for understand- ing applications of NMR to QIP and explain their current successes, limitations and potential. NMR spectroscopy is well known for its wealth of diverse coherent manipulations of spin dynamics. Ideas and instrumentation from liquid state NMR spectroscopy have been used to experiment with QIP. This approach has carried the field to a complexity of about 10 qubits, a small number for quantum compu- tation but large enough for observing and better understanding the complexity of the quantum world. While liquid state NMR is the only present-day technology about to reach this number of qubits, further increases in complexity will require new methods. We sketch one direction leading towards a scalable quantum computer using spin 1/2 particles. The next step of which is a solid state NMR-based QIP capable of reaching 10-30 qubits.