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A Brief History and Current Research

Fifty Years of Solid State NMR
I was born and raised in the lumber mills and hockey rinks of New Westminster, near Vancouver, British Columbia, Canada. I did my B.Sc., M.Sc., and Ph.D. in the Physics Department at the University of British Columbia (1965-1975). My principal thesis work involved using gas phase nuclear magnetic resonance relaxation techniques to better understand the quantum mechanical rotational structure of the methane molecule and the effects of collisions. I did a Postdoctoral Fellowship in Nottingham, England (1975-1977) where I looked for Robin Hood and Maid Marian and studied the quantum mechanical tunneling of intramolecular atomic groups at low temperatures using electron spin and nuclear spin relaxation techniques. I joined the Physics Department at Bryn Mawr College in 1977 and retired 40 years later in 2017. At Bryn Mawr, my students, my collaborators, and I studied the relationship between structure and motion in molecular solids using solid state nuclear spin-lattice relaxation techniques. We performed variable-temperature (77–370 K) and variable-frequency (8.50, 22.5, and 53.0 MHz) solid state 1H (proton) and 19F (fluorine) nuclear magnetic resonance (NMR) spin-lattice relaxation experiments in organic van der Waals solids to study the intramolecular rotation of methyl (CH3) and fluoromethyl (CF3) groups. The distinguishing feature of the experiments was the very low NMR frequencies needed in the nuclear spin relaxation experiments to investigate the motions. The overall goal was to develop complete and consistent compound-independent models for the intramolecular motions in these systems and determine how these motions related to the molecular and crystal structure. The work was complemented by the work of others at Bryn Mawr and other institutions doing compound synthesis and purification, ab initio electronic structure calculations, field emission scanning electron microscopy, single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and high-resolution 1H and 19F NMR spectroscopy. In sabbatical leaves at the University of Southampton (England) and the University of British Columbia (Vancouver) I did 2H (deuteron) NMR spectroscopy and relaxation in liquid crystals. From 1997 to 2007 I was a Visiting Research Professor at the University of Delaware working in the group of Cecil Dybowski. We performed difficult and unusual nuclear spin relaxation and NMR spectroscopy experiments using the 111Cd (cadmium), 113Cd, 119Sn (tin), and 207Pb (lead) nuclei as probes of motion, structure, and fundamental interactions in a variety of atomic solids. This almost five decades of research is discussed in 83 publications whose url's are available on the Bryn Mawr College website (Google "Bryn Mawr College Emeritus Faculty").

Recent Publications

83. Concomitant Polymorphism in an Organic Solid: Molecular and Crystal Structure and Intramolecular and Intermolecular Potential Contributions to tert-Butyl and Methyl Group Rotation. P A Beckmann, P R Rablen, J Schmink, S T Szewczyk, and A L Rheingold 2019 ChemPhysChem, 20 2887-2894. <;

82. Proton spin-lattice relaxation in methylphenanthrenes IV: 1,4-dimethylphenanthrene. P A Beckmann 2019 Journal of Chemical Physics 50 124508 1-3. <;

81. H-1 Spin-Lattice Relaxation in Organic Molecular Solids: Polymorphism and the Dependence on Sample Preparation, P A Beckmann, J Ford, W P Malachowski, A R McGhie, C E Moore, A L Rheingold, G J Sloan, and S T Szewczyk 2018 ChemPhysChem 19 2423-2436. <;

80. Note: Methyl and t-butyl group rotation in van der Waals solids. P A Beckmann, A L Rheingold, and J Schmink 2018 Journal of Chemical Physics 148 106101 1-2. <;

79. Solid-solid Phase Transitions and t-Butyl and Methyl Group Rotation in an Organic Solid: X-ray Diffractometry, Differential Scanning Calorimetry, and Solid State H-1 Nuclear Spin Relaxation. P A Beckmann, A R McGhie, A L Rheingold, G J Sloan, and S T Szewczyk 2017 Journal of Physical Chemistry A 2017 121 6220-6230. <;

78. Monitoring a simple hydrolysis process in an organic solid by observing methyl group rotation. P A Beckmann, J M Bohen, J Ford, W P Malachowski, C W Mallory, F B Mallory, A R McGhie, A L Rheingold, G J Sloan, S T Szewczyk, X Wang, and K A Wheeler 2017 Solid State Nuclear Magnetic Resonance 85 1-11. <;

77. H-1 and F-19 spin-lattice relaxation and CH3 or CF3 reorientation in molecular solids containing both H and F atoms. P A Beckmann and A L Rheingold 2016 Journal of Chemical Physics, 144 154308 1-12. <;

76. Methyl and t-butyl group rotation in a molecular solid: 1H NMR spin-lattice relaxation and X-ray diffraction. P A Beckmann, C E Moore, and A L Rheingold 2016 Physical Chemistry Chemical Physics, 18 1720-1726. < - !divAbstract>

75. Nonexponential 1H spin-lattice relaxation and methyl group rotation in molecular solids. P. A. Beckmann 2015 Solid State Nuclear Magnetic Resonance 71 91-95. <;

74. Methoxy and methyl group rotation: Solid state NMR 1H spin-lattice relaxation, electronic structure alculations, X-ray diffractometry, and scanning electronic microscopy. P A Beckmann, C W Mallory, F B Mallory, A L Rheingold, and X Wang 2015 ChemPhysChem 16 1509-1519. <;