- Email: [email protected]
Introduction to the special issue in honor of Regents' Prof. John C.H. Spence in occasion of his 65th birthday
Ultramicroscopy 111 (2011) 745–746
Contents lists available at ScienceDirect
Ultramicroscopy journal homepage: www.elsevier.com/locate/ultramic
Editorial
Introduction to the special issue in honor of Regents’ Prof. John C.H. Spence in occasion of his 65th birthday
This special issue, dedicated to John C.H. Spence on the occasion of his 65th birthday, contains original work by colleagues, who have enjoyed the privilege of working and/or collaborating with him and who wish to express their thanks and appreciation with a highlight of their own research. John Spence studied Physics at Melbourne University, Australia. During his Ph.D. study in the early 1970s with Alan Spargo, John worked on electron energy loss spectroscopy (EELS), a technique invented in the early days of electron microscopy but only becoming popular in the 1980s with widely available commercial spectrometers. Shortly after, together with D.W. Johnson, John developed the logarithmic deconvolution method for removing multiple scattering from energy-loss spectra, now an essential tool for any quantitative EELS analysis. As a post-doctoral fellow at Oxford University, working with Mike Whelan, Sir Peter Hirsch and David Cockayne, John started to work on the theory of dynamical scattering and image formation in TEM with the aim to see single atoms. Moving to John Cowley’s group in 1976 at Arizona State University, his early years there were devoted to the theory of STEM imaging (which at that time was still a very new microscopy technique) electron channeling and its application for locating foreign atoms in crystals (ALCHEMI, with Johan Tafto) and the first observations of coherent Bremstrahlung in EDX spectra. 0304-3991/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ultramic.2011.03.017
746
Editorial / Ultramicroscopy 111 (2011) 745–746
In the early 1980s John attached, together with N. Yamamoto, a cathodoluminescence detector to a Philips EM 400 T, recording polarization-specific CL spectra and fixed-wavelength CL images of individual dislocations in diamond samples. He also built an early intensified video system, from which later, in 1988, he developed, together with Jian-Min Zuo, perhaps the first direct-recording CCD camera for TEM. A major and productive part of his research in the 1980s was focused on HRTEM studies of defects in semiconductors, including the famous ‘‘shuffle or glide’’ question for dislocation cores in silicon. Later John employed a number of very different approaches to study extended defects by performing very early DFT calculations of crack propagation, observing, together with Harry Kolar, moving dislocation kinks along partial dislocations by taking advantage of forbidden FCC reflections for TEM imaging, and explored methods for the elucidation of the core structure of dislocations by electron microdiffraction. Starting in the mid-1980s, John became interested in the possibility of developing convergent-beam electron diffraction (CBED) into a quantitative technique for mapping crystal charge density distributions with great accuracy, leading to a long and fruitful collaboration with Jian-Min Zuo and Mike O’Keefe culminating in 1999 in a Nature paper reporting the ‘direct observation’ of atomic d-orbitals. Encouraged by the success of quantitative CBED, John also started to investigate various mathematical approaches to solve the dynamic inversion problem for determining unknown crystal structures directly in the early 1990s. In the late 1980s and early 1990s John enthusiastically engaged himself in developing experimental apparatuses for novel condensed matter physics experiments. He developed the first STM inside a TEM sample holder with William Lo for simultaneous STM and TEM observations. He then combined, together with Uwe Weierstall, a scanning tunneling microscope (STM) with a time-of-flight spectrometer for identifying atomic species. During this period, he also developed a low voltage point-projection microscope with Uwe Weierstall and students. These instrument building efforts were followed by recent developments of new coherent electron sources as well as injectors for spraying beams of individual molecules across electron and X-ray beams. One of the physical phenomena having increasingly influenced John’s research throughout the past decades is spatial coherence, particularly its potential to overcome some limitations of direct imaging. In the early 1990s, together with Mike Scheinfein he investigated field emission from nanometer diameter electron sources, investigated the coherence properties of inelastically scattered electrons with Dirk van Dyck and Hannes Lichte, proposed, together with Christoph Koch, internal source holography, and has also imaged tobacco mosaic viruses at voltages as low as 40 V by point projection holography together with Uwe Weierstall. Spatial coherence is an essential requirement for coherent diffractive imaging (CDI) to which John is devoting most of his current research efforts, having become its passionate advocate and a well-respected protagonist in this field. With Malcolm Howells, John built an apparatus to record coherent X-ray diffraction patterns at the Advanced Light Source, in Lawrence Berkeley National Laboratory where John is also affiliated. In 2001, John led the organization of the first workshop on ‘‘new approaches to the phase problem for nonperiodic objects’’. This conference provided the theoretical basis and motivation for the rapid development of CDI using X-rays and electrons, and continues today as the successful ‘‘Coherence’’ workshops. Together with Stefano Marchesini and Henry Chapman, John developed the shrink-wrap method for X-ray CDI using only information from diffraction patterns. John was also one of the first to ¨ recognize the simplicity and power of the so-called charge flipping method proposed by Oszla´nyi and Suto in 2004 and helped to popularize its applications. Together with Jinsong Wu and Mike O’Keeffe, John applied charge flipping to X-ray powder diffraction data, which by now has become a powerful technique for solving unknown crystal structures. With the same enthusiasm for novel ideas that John has demonstrated throughout his career, he has become a leader in the emerging field of femtosecond protein nanocrystallography. This activity started naturally with his interest in CDI and new algorithms for inverting coherent electron or X-ray diffraction patterns, and his early attempts with Petra Fromme to record diffraction from laser-aligned molecules flowing across an X-ray beam, as well as protein powder diffraction from nanocrystals in flowing suspensions. This research has now exploded with the development of free electron laser (FEL) facilities. His recent experiments with Petra Fromme, Janos Hajdu, Ilme Schlichting, Henry Chapman and many others, at the Stanford Linac Coherent Light Source (LCLS) facility, were very recently published in two back-to-back papers in Nature. With Malcolm Howells he revived a 40-year old idea of obtaining structural information from crosscorrelations of diffracted intensities, which may now be possible with the short pulses of FELs. He is currently heavily involved with the design of several new experimental setups for femtosecond X-ray diffraction experiments at LCLS, the ultimate aim of which is the reconstruction of the time-dependent structure of individual protein molecules (molecular movies). His impact in this new field was highlighted in a workshop John himself organized in January 2011 in Berkeley. Just about every talk over the four-day ‘‘Biology with FELs’’ workshop referred to John’s ideas, inventions, or results. In addition to more than 400 journal articles in the many areas of condensed matter and diffraction physics mentioned above, John is also author of monographs on High Resolution Electron Microscopy (the 3rd edition has recently been published) and (with Jian-Min Zuo) on Electron Microdiffraction. With admiration for all of his achievements, we have assembled this special issue in honor of John Spence, intending it to highlight, rather than to represent, the diversity of areas that John has worked in. The topics range from coherent and incoherent imaging with elastically or inelastically scattered and even secondary electrons to theoretical and very practical aspects of electron and X-ray diffraction of crystals and individual molecules. Happy Birthday, John!
Guest editors Christoph T. Koch, Jian-Min Zuo, Henry Chapman E-mail address: [email protected] (C.T. Koch)
Contents lists available at ScienceDirect
Ultramicroscopy journal homepage: www.elsevier.com/locate/ultramic
Editorial
Introduction to the special issue in honor of Regents’ Prof. John C.H. Spence in occasion of his 65th birthday
This special issue, dedicated to John C.H. Spence on the occasion of his 65th birthday, contains original work by colleagues, who have enjoyed the privilege of working and/or collaborating with him and who wish to express their thanks and appreciation with a highlight of their own research. John Spence studied Physics at Melbourne University, Australia. During his Ph.D. study in the early 1970s with Alan Spargo, John worked on electron energy loss spectroscopy (EELS), a technique invented in the early days of electron microscopy but only becoming popular in the 1980s with widely available commercial spectrometers. Shortly after, together with D.W. Johnson, John developed the logarithmic deconvolution method for removing multiple scattering from energy-loss spectra, now an essential tool for any quantitative EELS analysis. As a post-doctoral fellow at Oxford University, working with Mike Whelan, Sir Peter Hirsch and David Cockayne, John started to work on the theory of dynamical scattering and image formation in TEM with the aim to see single atoms. Moving to John Cowley’s group in 1976 at Arizona State University, his early years there were devoted to the theory of STEM imaging (which at that time was still a very new microscopy technique) electron channeling and its application for locating foreign atoms in crystals (ALCHEMI, with Johan Tafto) and the first observations of coherent Bremstrahlung in EDX spectra. 0304-3991/$ - see front matter & 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ultramic.2011.03.017
746
Editorial / Ultramicroscopy 111 (2011) 745–746
In the early 1980s John attached, together with N. Yamamoto, a cathodoluminescence detector to a Philips EM 400 T, recording polarization-specific CL spectra and fixed-wavelength CL images of individual dislocations in diamond samples. He also built an early intensified video system, from which later, in 1988, he developed, together with Jian-Min Zuo, perhaps the first direct-recording CCD camera for TEM. A major and productive part of his research in the 1980s was focused on HRTEM studies of defects in semiconductors, including the famous ‘‘shuffle or glide’’ question for dislocation cores in silicon. Later John employed a number of very different approaches to study extended defects by performing very early DFT calculations of crack propagation, observing, together with Harry Kolar, moving dislocation kinks along partial dislocations by taking advantage of forbidden FCC reflections for TEM imaging, and explored methods for the elucidation of the core structure of dislocations by electron microdiffraction. Starting in the mid-1980s, John became interested in the possibility of developing convergent-beam electron diffraction (CBED) into a quantitative technique for mapping crystal charge density distributions with great accuracy, leading to a long and fruitful collaboration with Jian-Min Zuo and Mike O’Keefe culminating in 1999 in a Nature paper reporting the ‘direct observation’ of atomic d-orbitals. Encouraged by the success of quantitative CBED, John also started to investigate various mathematical approaches to solve the dynamic inversion problem for determining unknown crystal structures directly in the early 1990s. In the late 1980s and early 1990s John enthusiastically engaged himself in developing experimental apparatuses for novel condensed matter physics experiments. He developed the first STM inside a TEM sample holder with William Lo for simultaneous STM and TEM observations. He then combined, together with Uwe Weierstall, a scanning tunneling microscope (STM) with a time-of-flight spectrometer for identifying atomic species. During this period, he also developed a low voltage point-projection microscope with Uwe Weierstall and students. These instrument building efforts were followed by recent developments of new coherent electron sources as well as injectors for spraying beams of individual molecules across electron and X-ray beams. One of the physical phenomena having increasingly influenced John’s research throughout the past decades is spatial coherence, particularly its potential to overcome some limitations of direct imaging. In the early 1990s, together with Mike Scheinfein he investigated field emission from nanometer diameter electron sources, investigated the coherence properties of inelastically scattered electrons with Dirk van Dyck and Hannes Lichte, proposed, together with Christoph Koch, internal source holography, and has also imaged tobacco mosaic viruses at voltages as low as 40 V by point projection holography together with Uwe Weierstall. Spatial coherence is an essential requirement for coherent diffractive imaging (CDI) to which John is devoting most of his current research efforts, having become its passionate advocate and a well-respected protagonist in this field. With Malcolm Howells, John built an apparatus to record coherent X-ray diffraction patterns at the Advanced Light Source, in Lawrence Berkeley National Laboratory where John is also affiliated. In 2001, John led the organization of the first workshop on ‘‘new approaches to the phase problem for nonperiodic objects’’. This conference provided the theoretical basis and motivation for the rapid development of CDI using X-rays and electrons, and continues today as the successful ‘‘Coherence’’ workshops. Together with Stefano Marchesini and Henry Chapman, John developed the shrink-wrap method for X-ray CDI using only information from diffraction patterns. John was also one of the first to ¨ recognize the simplicity and power of the so-called charge flipping method proposed by Oszla´nyi and Suto in 2004 and helped to popularize its applications. Together with Jinsong Wu and Mike O’Keeffe, John applied charge flipping to X-ray powder diffraction data, which by now has become a powerful technique for solving unknown crystal structures. With the same enthusiasm for novel ideas that John has demonstrated throughout his career, he has become a leader in the emerging field of femtosecond protein nanocrystallography. This activity started naturally with his interest in CDI and new algorithms for inverting coherent electron or X-ray diffraction patterns, and his early attempts with Petra Fromme to record diffraction from laser-aligned molecules flowing across an X-ray beam, as well as protein powder diffraction from nanocrystals in flowing suspensions. This research has now exploded with the development of free electron laser (FEL) facilities. His recent experiments with Petra Fromme, Janos Hajdu, Ilme Schlichting, Henry Chapman and many others, at the Stanford Linac Coherent Light Source (LCLS) facility, were very recently published in two back-to-back papers in Nature. With Malcolm Howells he revived a 40-year old idea of obtaining structural information from crosscorrelations of diffracted intensities, which may now be possible with the short pulses of FELs. He is currently heavily involved with the design of several new experimental setups for femtosecond X-ray diffraction experiments at LCLS, the ultimate aim of which is the reconstruction of the time-dependent structure of individual protein molecules (molecular movies). His impact in this new field was highlighted in a workshop John himself organized in January 2011 in Berkeley. Just about every talk over the four-day ‘‘Biology with FELs’’ workshop referred to John’s ideas, inventions, or results. In addition to more than 400 journal articles in the many areas of condensed matter and diffraction physics mentioned above, John is also author of monographs on High Resolution Electron Microscopy (the 3rd edition has recently been published) and (with Jian-Min Zuo) on Electron Microdiffraction. With admiration for all of his achievements, we have assembled this special issue in honor of John Spence, intending it to highlight, rather than to represent, the diversity of areas that John has worked in. The topics range from coherent and incoherent imaging with elastically or inelastically scattered and even secondary electrons to theoretical and very practical aspects of electron and X-ray diffraction of crystals and individual molecules. Happy Birthday, John!
Guest editors Christoph T. Koch, Jian-Min Zuo, Henry Chapman E-mail address: [email protected] (C.T. Koch)