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First measurements of the differential positronium-formation cross-sections

Positrons are the antimatter version of electrons and so their fate in a matter world is ultimately to annihilate. However, prior to this, a positron may combine with an electron to form a matter-antimatter hybrid called positronium. This is akin to a hydrogen atom with the proton replaced by a positron. Fundamental to our understanding of the physical universe, positron and positronium are these days also acknowledged as being fantastically useful in practical applications such as probing material properties and medical diagnostics. However, there is still much that we do not know for sure about the details of the interactions of these particles with ordinary matter. For example if, in a collision with an atom or molecule, a positron captures an electron, in which directions is the positronium likely to travel and with what probability? More...

Published: Jun 17, 2015 12:35:19 PM

CO2 Satellite

New calculations to improve carbon dioxide monitoring from space

How light of different colours is absorbed by carbon dioxide (CO2) can now be accurately predicted using new calculations developed by a UCL-led team of scientists. This will help climate scientists studying Earth’s greenhouse gas emissions to better interpret data collected from satellites and ground stations measuring CO2. More...

Published: Jun 15, 2015 10:29:10 AM

Watt Steam Engine

On quantum scales, there are many second laws of thermodynamics

New research from UCL has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are generally not noticeable except on very small scales, at which point, they become increasingly important. More...

Published: Feb 10, 2015 11:55:53 AM



  1. J. Palmer and S. D. Hogan, "Experimental demonstration of a Rydberg-atom beam splitter", Phys. Rev. A, 95, 053413 (2017) DOI:10.1103/PhysRevA.95.053413
  2. A. M. Alonso, B. S. Cooper, A. Deller, L. Gurung, S. D. Hogan and D. B. Cassidy, "Velocity selection of Rydberg positronium using a curved electrostatic guide", Phys. Rev. A, 95, 053409 (2017) DOI:10.1103/PhysRevA.95.053409
  3. V. Zhelyazkova and S. D. Hogan, "Electrically tuned Förster resonances in collisions of NH3 with Rydberg helium atoms", Phys. Rev. A, 95, 042710 (2017) DOI:10.1103/PhysRevA.95.042710
  4. A. M. Alonso, S. D. Hogan and D. B. Cassidy, "Production of 2 3S1 positronium atoms by single-photon excitation in an electric field", Phys. Rev. A, 95, 033408 (2017) DOI:10.1103/PhysRevA.95.033408


  1. V. Zhelyazkova, R. Jirschik and S. D. Hogan, "Mean-field energy-level shifts and dielectric properties of strongly polarized Rydberg gases", Phys. Rev. A, 94, 053418 (2016) DOI:10.1103/PhysRevA.94.053418
  2. V. Zhelyazkova and S. D. Hogan, "Preparation of circular Rydberg states in helium using the crossed-fields method", Phys. Rev. A, 94, 023415 (2016) DOI:10.1103/PhysRevA.94.023415
  3. A. Deller, A. M. Alonso, B. S. Cooper, S. D. Hogan and D. B. Cassidy, "Electrostatically guided Rydberg positronium", Phys. Rev. Lett., 117, 073202 (2016) DOI:10.1103/PhysRevLett.117.073202
  4. P. Lancuba and S. D. Hogan, "Electrostatic trapping and in situ detection of Rydberg atoms above chip-based transmission lines", J. Phys. B: At. Mol. Opt. Phys., 49, 074006 (2016) DOI:10.1088/0953-4075/49/7/074006
  5. A. Deller, A. M. Alonso, B. S. Cooper, S. D. Hogan and D. B. Cassidy, "Measurement of Rydberg positronium fluorescence lifetimes", Phys. Rev. A, 93, 062513 (2016) DOI:10.1103/PhysRevA.93.062513
  6. S. D. Hogan, "Rydberg-Stark deceleration of atoms and molecules", EPJ Techniques and Instrumentation, 3, 1 (2016) DOI:10.1140/epjti/s40485-015-0028-4
  7. A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan and D. B. Cassidy, "Positronium decay from n = 2 states in electric and magnetic fields", Phys. Rev. A, 93, 012506 (2016) DOI:10.1103/PhysRevA.93.012506


  1. V. Zhelyazkova and S. D. Hogan, "Rydberg-Stark states in oscillating electric fields", Mol. Phys., 113, 3979 (2015) DOI:10.1080/00268976.2015.1098741
  2. A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan and D. B. Cassidy, "Controlling positronium annihilation with electric fields", Phys. Rev. Lett., 115, 183401 (2015) DOI:10.1103/PhysRevLett.115.183401
  3. V. Zhelyazkova and S. D. Hogan, "Probing interactions between Rydberg atoms with large electric dipole moments in amplitude-modulated electric fields", Phys. Rev. A, 92, 011402(R) (2015) DOI:10.1103/PhysRevA.92.011402
  4. T. E. Wall, A. M. Alonso, B. S. Cooper, A. Deller, S. D. Hogan and D. B. Cassidy, "Selective production of Rydberg-Stark states of positronium", Phys. Rev. Lett., 114, 173001 (2015) DOI:10.1103/PhysRevLett.114.173001


  1. T. E. Wall, D. B. Cassidy and S. D. Hogan, "Single-color two-photon spectroscopy of Rydberg states in electric fields", Phys. Rev. A, 90, 053430 (2014) DOI:10.1103/PhysRevA.90.053430
  2. P. Lancuba and S. D. Hogan, "Transmission-line decelerators for atoms in high Rydberg states", Phys. Rev. A, 90, 053420 (2014) DOI:10.1103/PhysRevA.90.053420
  3. H. Ko and S. D. Hogan, "High-field-seeking Rydberg atoms orbiting a charged wire", Phys. Rev. A89, 053410 (2014) DOI:10.1103/PhysRevA.89.053410
  4. D. B. Cassidy and S. D. Hogan, "Atom control and gravity measurements using Rydberg positronium", Int. J. Mod. Phys. Conf. Ser.30, 1460259 (2014) DOI:10.1142/S2010194514602592


  1. P. Lancuba and S. D. Hogan, "Guiding Rydberg atoms above surface-based transmission lines", Phys. Rev. A88, 043427 (2013) DOI:10.1103/PhysRevA.88.043427
  2. S. D. Hogan, "Calculated photoexcitation spectra of positronium Rydberg states",Phys. Rev. A87, 063423 (2013) DOI:10.1103/PhysRevA.87.063423
  3. S. D. Hogan, Ch. Seiler and F. Merkt, "Motional, isotope and quadratic Stark effects in Rydberg-Stark deceleration and electric trapping of H and D", J. Phys. B: At. Mol. Opt. Phys., 46, 045303 (2013) DOI:10.1088/0953-4075/46/4/045303


  1. S. D. Hogan, J. A. Agner, F. Merkt, T. Thiele, S. Filipp and A. Wallraff, "Driving Rydberg-Rydberg transitions from a co-planar microwave  waveguide", Phys. Rev. Lett. 108, 063004 (2012) DOI:10.1103/PhysRevLett.108.063004
  2. S. D. Hogan, P. Allmendinger, H. Saßmannshausen, H. Schmutz and F. Merkt, "A surface-electrode Rydberg-Stark decelerator", Phys. Rev. Lett. 108, 063008 (2012) DOI:10.1103/PhysRevLett.108.063008
  3. Ch. Seiler, S. D. Hogan and F. Merkt, "Dynamical processes in Rydberg-Stark  deceleration and trapping of atoms and molecules", Chimia 66, 208 (2012) DOI:10.2533/chimia.2012.208
  4. S. D. Hogan, "Cold atoms and molecules by Zeeman deceleration and Rydberg-Stark deceleration", Habilitation Thesis, Laboratory of Physical Chemistry, ETH Zurich (2012) [download pdf (33 MB)]


  1. S. D. Hogan, M. Motsch and F. Merkt, "Deceleration of supersonic beams using inhomogeneous electric and magnetic fields", Phys. Chem. Chem. Phys. 13, 18705 (2011) DOI:10.1039/C1CP21733J
  2. Ch. Seiler, S. D. Hogan and F. Merkt, "Trapping cold molecular hydrogen", Phys. Chem. Chem. Phys. 13, 19000 (2011) DOI:10.1039/C1CP21276A
  3. Ch. Seiler, S. D. Hogan, H. Schmutz, J. A. Agner and F. Merkt, "Collisional and radiative processes in adiabatic deceleration, deflection and off-axis trapping of a Rydberg atom beam", Phys. Rev. Lett. 106, 073003 (2011) DOI:10.1103/PhysRevLett.106.073003
  4. A. W. Wiederkehr, M. Motsch, S. D. Hogan, M. Andrist, H. Schmutz, B. Lambillotte, J. A. Agner and F. Merkt, "Multistage Zeeman deceleration of metastable neon", J. Chem. Phys. 135, 214202 (2011) DOI:10.1063/1.3662141


  1. A. W. Wiederkehr, S. D. Hogan, B. Lambillotte, M. Andrist, H. Schmutz, J. Agner, Y. Salathé and F. Merkt, "Trapping deuterium atoms", Phys. Rev. A 81, 021402(R) (2010) DOI:10.1103/PhysRevA.81.021402
  2. A. W. Wiederkehr, S. D. Hogan and F. Merkt, "Phase stability in a multistage Zeeman decelerator", Phys. Rev. A 82, 043428 (2010) DOI:10.1103/PhysRevA.82.043428


  1. S. D. Hogan, Ch. Seiler and F. Merkt, "Rydberg-state-enabled deceleration and trapping of cold molecules", Phys. Rev. Lett. 103, 123001 (2009) DOI:10.1103/PhysRevLett.103.123001
  2. S. D. Hogan and F. Merkt, "A New Perspective on the Binding Power of an Electron", ChemPhysChem 10, 2931 (2009) DOI:10.1002/cphc.200900499


  1. S. D. Hogan and F. Merkt, "Demonstration of Three-Dimensional Electrostatic Trapping of State-Selected Rydberg Atoms", Phys. Rev. Lett. 100, 043001 (2008) DOI:10.1103/PhysRevLett.100.043001
  2. S. D. Hogan, E. Vliegen, D. Sprecher, N. Vanhaecke, M. Andrist, H. Schmutz, U. Meier, B. H. Meier and F. Merkt, "Stark and Zeeman deceleration of neutral atoms and molecules" in "Laser Spectroscopy. Proceedings of the XVIII International Conference ICOLS 2007" Leo Hollberg (ed.), Jim Bergquist (ed.) and Mark Kasevich (ed.) World Scientific, Singapore, 153-166 (2008) DOI:10.1142/9789812813206_0013
  3. S. D. Hogan, A. W. Wiederkehr, M. Andrist, H. Schmutz and F. Merkt, "Slow beams of atomic hydrogen by multistage Zeeman deceleration", J. Phys. B: At. Mol. Opt. Phys. 41, 081005 (2008) DOI:10.1088/0953-4075/41/8/081005
  4. S. D. Hogan, A. W. Wiederkehr, H. Schmutz and F. Merkt, "Magnetic trapping of hydrogen after multistage Zeeman deceleration", Phys. Rev. Lett. 101, 143001 (2008) DOI:10.1103/PhysRevLett.101.143001
  5. J.-P. Connerade, S. D. Hogan, H.-P. Liu and M.-S. Zhan, "Towards a test of sting theory using Rydberg atoms", Eur. Phys. J. D 46, 431 (2008) DOI:10.1140/epjd/e2007-00335-x
  6. A. Kellerbauer, M. Amoretti, A. S. Belov, G. Bonomi, I. Boscolo, R. S. Brusa, M. Büchner, V. M. Byakov, L. Cabaret, C. Canali, C. Carraro, F. Castelli, S. Cialdi, M. de Combarieu, D. Comparat, G. Consolati, N. Djourelov, M. Doser, G. Drobychev, A. Dupasquier, G. Ferrari, P. Forget, L. Formaro, A. Gervasini, M. G. Giammarchi, S. N. Gninenko, G. Gribakin, S. D. Hogan, M. Jacquey, V. Lagomarsino, G. Manuzio, S. Mariazzi, V. A. Matveev, J. O. Meier, F. Merkt, P. Nedelec, M. K. Oberthaler, P. Pari, M. Prevedelli, F. Quasso, A. Rotondi, D. Sillou, S. V. Stepanov, H. H. Stroke, G. Testera, G. M. Tino, G. Trénec, A. Vairo, J. Vigué, H. Walters, U. Warring, S. Zavatarelli and D. S. Zvezhinskij, "Proposed antimatter gravity measurement with an antihydrogen beam", Nucl. Instr. and Meth. in Phys. Res. B 266, 351 (2008) DOI:10.1016/j.nimb.2007.12.010


  1. S. D. Hogan, D. Sprecher, M. Andrist, N. Vanhaecke and F. Merkt, "Zeeman deceleration of H and D", Phys. Rev. A 76, 023412 (2007) DOI:10.1103/PhysRevA.76.023412
  2. E. Vliegen, S. D. Hogan, H. Schmutz and F. Merkt, "Stark deceleration and trapping of hydrogen Rydberg atoms", Phys. Rev. A 76, 023405 (2007) DOI:10.1103/PhysRevA.76.023405
  3. J.-P. Connerade, S. D. Hogan, A. M. Abdulla and M. S. Zhan, "Highly excited atoms - a homage to Pierre Jacquinot", Phys. Scr. 76, C140 (2007) DOI:10.1088/0031-8949/76/4/N06
  4. S. D. Hogan and J.-P. Connerade, "On the effect of resolution on nearest-neighbour level spacings in atomic spectra", Eur. Phys. J. D 44, 47 (2007) DOI:10.1140/epjd/e2007-00165-x


  1. S. D. Hogan, "Rydberg states interacting in crossed electric and magnetic fields", PhD Thesis, Department of Physics, Imperial College London (2006)
  2. H. P. Liu, Z. G. Sun, S. D. Hogan and N. Q. Lou, "Photodissociation dynamics of CF3I investigated by two-color femtosecond laser pulses", Eur. Phys. J. D 40, 357 (2006) DOI:10.1140/epjd/e2006-00183-2


  1. S. Gundry, M. P. Anscombe, A. M. Abdulla, S. D. Hogan, E. Sali, J. W. G. Tisch, and J. P. Marangos, "Off-resonant preparation of a vibrational coherence for enhanced stimulated Raman scattering", Phys. Rev. A 72, 033824 (2005) DOI:10.1103/PhysRevA.72.033824
  2. J.-P. Connerade, S. D. Hogan and A. M. Abdulla, "Experimental investigation of atoms in crossed electric and magnetic fields", J. Phys. B: At. Mol. Opt. Phys. 38 S141 (2005) DOI:10.1088/0953-4075/38/2/011


  1. A. M. Abdulla, S. Hogan, M. S. Zhan and J.-P. Connerade, "High-lying Rydberg states of barium in crossed fields", J. Phys. B: At. Mol. Opt. Phys. 37 L147 (2004) DOI:10.1088/0953-4075/37/8/L01