Ultrahigh-resolution Spectroscopy Research Articles

Prospect of ultrahigh-resolution fast neutron absorption spectroscopy based on a laser plasma electron accelerator

Abstract Fast neutron absorption spectroscopy is widely used in the study of nuclear structure and element analysis. However, due to the traditional neutron source pulse duration being of the order of nanoseconds, it is difficult to obtain a high-resolution absorption spectrum. Thus, we present a method of ultrahigh energy-resolution absorption spectroscopy via a high repetition rate, picosecond duration pulsed neutron source driven by a terawatt laser. The technology of single neutron count is used, which results in easily distinguishing the width of approximately 20 keV at 2 MeV and an asymmetric shape of the neutron absorption peak. The absorption spectroscopy based on a laser neutron source has one order of magnitude higher energy-resolution power than the state-of-the-art traditional neutron sources, which could be of benefit for precisely measuring nuclear structure data.

Nodeless electron pairing in CsV3Sb5-derived kagome superconductors.

The newly discovered kagome superconductors represent a promising platform for investigating the interplay between band topology, electronic order and lattice geometry1-9. Despite extensive research efforts on this system, the nature of the superconducting ground state remains elusive10-17. In particular, consensus on the electron pairing symmetry has not been achieved so far18-20, in part owing to the lack of a momentum-resolved measurement of the superconducting gap structure. Here we report the direct observation of a nodeless, nearly isotropic and orbital-independent superconducting gap in the momentum space of two exemplary CsV3Sb5-derived kagome superconductors-Cs(V0.93Nb0.07)3Sb5 and Cs(V0.86Ta0.14)3Sb5-using ultrahigh-resolution and low-temperature angle-resolved photoemission spectroscopy. Remarkably, such a gap structure is robust to the appearance or absence of charge order in the normal state, tuned by isovalent Nb/Ta substitutions of V. Our comprehensive characterizations of the superconducting gap provide indispensable information on the electron pairing symmetry of kagome superconductors, and advance our understanding of the superconductivity and intertwined electronic orders in quantum materials.

Solid-state NMR spectroscopy at ultrahigh resolution for structural and dynamical studies of MOFs

To characterize the structure and dynamics of metal–-organic frameworks (MOFs) in-depth at the molecular level, it is necessary to pursue high-resolution solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. Spectral resolution is usually affected by the quality of materials and various experimental conditions, of which magic angle (MA) accuracy is a crucial determinant. The current industrial criteria for MA calibration based on the common standard of KBr were found insufficient in guaranteeing optimal resolution MAS NMR for highly ordered MOFs. To drive towards higher-resolution MAS NMR spectroscopy, we propose a calibration protocol for more accurate MA with a higher-precision criterion based on 79Br MAS NMR of KBr, where the linewidth ratio of the fifth-order spinning sideband to the central band of KBr should be less than 1.00. As a result, ultrahigh-resolution 13C cross-polarization (CP) MAS NMR of MOF-5 is achieved with minimal linewidths as low as 4 Hz, and therefore MOF-5 can be used as a new standard convenient for verifying MA accuracy and also optimizing 13C CP conditions. Maintaining high-precision MA under variable temperature (VT) was found challenging on certain commercial MAS NMR probes, as was systematically investigated by VT NMR using KBr and MOF-5. Nevertheless, ultrahigh-resolution MAS NMR spectroscopy with stable MA under VT is employed to reveal fine structures and linker dynamics of a series of Zn-based MOFs with highly regulated structures. The ultrahigh-resolution NMR methodcan be generally applied to study a broad range of MOFs and other materials.

Unveiling the role of dissolved organic matter on phosphorus sorption and availability in a 5-year manure amended paddy soil.

Dissolved organic matter (DOM) is an active component of organic manure that is widely used in agroecosystems to increase nutrient availability and consequently enhance crop yields. However, the ways in which soil DOM characteristics are influenced by organic manure and how it contributes to crop yield and soil P availability remains unclear. Here, we conducted a 5-year field experiment and demonstrated that partial replacement of chemical P fertilizer with swine manure could maintain high rice yield and soil available P levels and increase P fertilizer use efficiency (PUE) in comparison to chemical fertilization, even when the total P input was reduced. This suggests that organic manure application can significantly mobilize soil P and increase P availability. Structural equation modeling analysis indicated that the soil pH and humification degree of DOM, rather than DOM content, directly decreased maximum P adsorption capacity. The combined results of the optical spectroscopy and ultrahigh-resolution mass spectroscopy obtained from the laboratory validation experiment based on the DOM-removed soil demonstrated that manure-derived DOM competing with P for adsorption was one of the main reasons for the increase in soil P availability and that the effective DOM components were N-containing lignins, tannins, and condensed polycyclic aromatics with higher O/C and lower H/C ratios. Overall, our results provide solid evidence that soil DOM characteristics are influenced by manure application and facilitate soil P availability, which could help guide the sustainable P management and manure application in agroecosystems.

Identification of microplastics and associated contaminants using ultra high resolution microscopic and spectroscopic techniques

The present study establishes a new procedure to characterize micro(nano)plastics (MNPs) and identify contaminants adhered to the plastic particles in aquatic environments by applying ultra-high resolution microscopy and spectroscopy techniques. Naturally fragmented microplastics (MPs) were collected from Manzanillo and Santiago Bays, Mexico and analyzed using: Confocal Laser Scanning Microscopy (CLSM), Fourier-Transform Infrared Spectroscopy (FTIR), μ-RAMAN, Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS) and Environmental Electron Scanning Microscopy (ESEM). The information obtained from each of these techniques was integrated to produce a comprehensive profile of each particle. Sample preparation was tested by applying three different rinses (unrinsed, distilled water and alcohol) to untreated MPs collected from Manzanillo Bay, finding that when large impurities are present an alcohol rinse makes it easier to examine the associated contaminants. Based on this emerging methodology, polyethylene and polypropylene MPs were identified with associated contaminants such as arsenic, cadmium, aluminum, and benzene. This study demonstrates the presence of pollutants that may be linked to MNPs in aquatic ecosystems and proposes an accurate relatively fast procedure for their analysis that does not require chemical extraction.

Ultrasensitive and ultrafast nonlinear optical characterization of surface plasmons

Amid the rapid development of nanosciences and nanotechnologies, plasmonics has emerged as an essential and fascinating discipline. Surface plasmons (SPs) lay solid physical foundations for plasmonics and have been broadly applied to ultrahigh-resolution spectroscopy, optical modulation, renewable energy, communication technology, etc. Sensitive optical characterizations for SPs, including far/near-field optics, spatial-resolved spectroscopy, and time-resolved behaviors of SPs, have prompted intense interest in diverse fields. In this Research Update, the ultrasensitive optical characterization for sub-radiant SPs is first introduced. Then, distinct characterization methods of nonlinear plasmonics, including plasmon-enhanced second harmonic generation and plasmon-enhanced sum frequency generation, are demonstrated in some classical nanostructures. Transient optical characterizations of SPs are also demonstrated in some well-defined nanostructures, enabling the deep realization of time-resolved behaviors. Finally, future prospects and efforts of optical characterization for SPs are proposed.

Spin-orbit splitting of Ar+ , Kr+ , and Kr2+ determined by strong-field ultrahigh-resolution Fourier-transform spectroscopy

The authors determine the spin-orbit-splitting energies in the electronic ground states of Ar${}^{+}$, Kr${}^{+}$, and Kr${}^{2+}$ from the temporal evolution of wave packets generated by strong-field ionization of the neutral atoms and the singly charged ion, respectively. The results are in agreement with earlier measurements with significantly improved precision.

Devices with Whispering Gallery Mode Optical Resonators: Current State of Research and Prospects for their Application in Time and Frequency Metrology

The development of highly stable, narrow-band laser sources and oscillators producing sets of equidistant narrow optical spectral lines (so-called optical frequency combs) constitutes one of the most urgent tasks in the metrological support of time and frequency measurements. These devices are necessary for the transmission of frequency reference signals, as well as for use in mobile sources of time and frequency reference signals in optical and microwave spectral ranges. Such devices are also used in precision, ultra-high resolution spectroscopy. A promising direction for the development of highly stable, narrow-band lasers and generation of optical frequency combs (OFCs) is the use of miniature whispering gallery mode (WGM) optical resonators. Recently, the properties of such resonators have been actively studied along with technologies for their production. This article presents a review of the current state of research into the use of WGM optical resonators in time and frequency metrology. The types, advantages, and disadvantages of WGM resonators, as well as methods for generating various signals, specifically microwave signals, are described. Examples of existing laboratory setups used by Russian and foreign scientific groups are given. The authors examine prospects for the further use of WGM resonators.

Unprecedented Surface Plasmon Modes in Monoclinic MoO2 Nanostructures.

Developing stable plasmonic materials featuring earth-abundant compositions with continuous band structures, similar to those of typical metals, has received special research interest. Owing to their metal-like behavior, monoclinic MoO2 nanostructures have been found to support stable and intense surface plasmon (SP) resonances. However, no progress has been made on their energy and spatial distributions over individual nanostructures, nor the origin of their possibly existing specific SP modes. Here, various MoO2 nanostructures are designed via polydopamine chemistry and managed to visualize multiple longitudinal and transversal SP modes supported by the monoclinic MoO2 , along with intrinsic interband transitions, using scanning transmission electron microscopy coupled with ultrahigh-resolution electron energy loss spectroscopy. The identified geometry-dependent SP energies are tuned by either controlling the shape and thickness of MoO2 nanostructures through their well-designed chemical synthesis, or by altering their length using a developed electron-beam patterning technique. Theoretical calculations reveal that the strong plasmonic behavior of the monoclinic MoO2 is associated with the abundant delocalized electrons in the Mo d orbitals. This work not only provides a significant improvement in imaging and tailoring SPs of nonconventional metallic nanostructures, but also highlights the potential of MoO2 nanostructures for micro-nano optical and optoelectronic applications.

Ultrahigh resolution spectroscopy for dimethyl sulfide at the ν1- and ν8-bands by a distributed feedback interband cascade laser

The ultrahigh-resolution, air-broadened mid-infrared absorption spectrum of dimethyl sulfide (DMS) was recorded in the spectral region of 2994.17–2999.03 cm−1, where the strong ν1-/ν8-bands are located. Benefitting from the tunable laser absorption spectrometry with a distributed feedback interband cascade laser, the spectral resolution achieved 5.69 × 10−6 cm−1. The recorded spectra of DMS are very close to that in the Pacific Northwest National Laboratory (PNNL) database, however it has a much lower absorbance uncertainty of 0.38%. And the maximum relative difference of the full width at half maximum and the integrated area of spectral peaks between the recorded spectra and the PNNL data are as large as 16.7% and 27.9%, respectively, which could mainly come from the difference of the spectral resolution. The more accurate reference spectrum is hopeful to be applied to absolute measurement and remote sensing for gaseous DMS.

Core-Shell Nanostructure-Enhanced Raman Spectroscopy for Surface Catalysis.

ConspectusThe rational design of highly efficient catalysts relies on understanding their structure-activity relationships and reaction mechanisms at a molecular level. Such an understanding can be obtained by in situ monitoring of dynamic reaction processes using surface-sensitive techniques. Surface-enhanced Raman spectroscopy (SERS) can provide rich structural information with ultrahigh surface sensitivity, even down to the single-molecule level, which makes it a promising tool for the in situ study of catalysis. However, only a few metals (like Au, Ag, and Cu) with particular nanostructures can generate strong SERS effects. Thus, it is almost impossible to employ SERS to study transition metals (like Pt, Pd, Ru, etc.) and other nonmetal materials that are usually used in catalysis (material limitation). Furthermore, SERS is also unable to study model single crystals with atomically flat surface structures or practical nanocatalysts (morphology limitation). These limitations have significantly hindered the applications of SERS in catalysis over the past four decades since its discovery, preventing SERS from becoming a widely used technique in catalysis. In this Account, we summarize the extensive efforts done by our group since the 1980s, particularly in the past decade, to overcome the material and morphology limitations in SERS. Particular attention has been paid to the work using core-shell nanostructures as SERS substrates, because they provide high Raman enhancement and are highly versatile for application on different catalytic materials. Different SERS methodologies for catalysis developed by our group, including the "borrowing" strategy, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS), and SHINERS-satellite strategy, are discussed in this account, with an emphasis on their principles and applications. These methodologies have successfully overcome the long-standing limitations of traditional SERS, enabling in situ tracking of catalysis at model single-crystal surfaces and practical nanocatalysts that can hardly be studied by SERS. Using these methodologies, we systematically studied a series of fundamentally important reactions, such as oxygen reduction reaction, hydrogen evolution reaction, electrooxidation, CO oxidation, and selective hydrogenation. As such, direct spectroscopic evidence of key intermediates that can hardly be detected by other traditional techniques was obtained. Combined with density functional theory and other in situ techniques, the reaction mechanisms and structure-activity relationships of these catalytic reactions were revealed at a molecular level. Furthermore, the future of SERS in catalysis has also been proposed in this work, which we believe should be focused on the in situ dynamic studies at the single-molecule, or even single-atom, level using techniques with ultrahigh sensitivity or spatial resolution, for example, single-molecule SERS or tip-enhanced Raman spectroscopy. In summary, core-shell nanostructure-enhanced Raman spectroscopies are shown to greatly boost the application of SERS in catalysis, from model systems like single-crystal surfaces to practical nanocatalysts, liquid-solid interfaces to gas-solid interfaces, and electrocatalysis to heterogeneous catalysis to photocatalysis. Thus, we believe this Account would attract increasing attention to SERS in catalysis and opens new avenues for catalytic studies.

State of the art and perspectives of the devices with the optical WGM resonators in time and frequency metrology

One of the most important tasks in the metrological support of time and frequency measurements is a development of an extremely stable narrow-bandwidth laser sources and oscillators of the sets of the equidistant narrow optical spectral lines (the so-called “optical combs”). These devices are necessary for the transmission of the reference frequency signals and for use as part of mobile sources of time and frequency reference signals in optical and microwave spectral ranges. They are also required for precision ultra-high resolution spectroscopy. A promising direction for the creation of highly stable narrow-band lasers and optical combs is the use of miniature optical whispering gallery modes resonators. Recently, research has been actively performed on the properties and manufacturing techniques of such resonators, as well as devices using them. The article provides a review of current research into applications of optical whispering gallery mode resonators in time and frequency metrology. Main advantages and disadvantages of such devices and prospects for their further use are discussed. The authors review in detail some examples of existing laboratory setups of Russian and foreign scientific groups.

Realization of wafer-scale nanogratings with sub-50 nm period through vacancy epitaxy

Gratings, one of the most important energy dispersive devices, are the fundamental building blocks for the majority of optical and optoelectronic systems. The grating period is the key parameter that limits the dispersion and resolution of the system. With the rapid development of large X-ray science facilities, gratings with periodicities below 50 nm are in urgent need for the development of ultrahigh-resolution X-ray spectroscopy. However, the wafer-scale fabrication of nanogratings through conventional patterning methods is difficult. Herein, we report a maskless and high-throughput method to generate wafer-scale, multilayer gratings with period in the sub-50 nm range. They are fabricated by a vacancy epitaxy process and coated with X-ray multilayers, which demonstrate extremely large angular dispersion at approximately 90 eV and 270 eV. The developed new method has great potential to produce ultrahigh line density multilayer gratings that can pave the way to cutting edge high-resolution spectroscopy and other X-ray applications.

Studying fundamental physics using quantum enabled technologies with trapped molecular ions

The text below was written during two visits that Daniel Segal made at Université Paris 13. Danny stayed at Laboratoire de Physique des Lasers the summers of 2008 and 2009 to participate in the exploration of a novel lead in the field of ultra-high resolution spectroscopy. Our idea was to probe trapped molecular ions using Quantum Logic Spectroscopy (QLS) in order to advance our understanding of a variety of fundamental processes in nature. At that time, QLS, a ground-breaking spectroscopic technique, had only been demonstrated with atomic ions. Our ultimate goals were new approaches to the observation of parity violation in chiral molecules and tests of time variations of the fundamental constants. This text is the original research proposal written eight years ago. We have added a series of notes to revisit it in the light of what has been since realized in the field.

Ultrahigh-Resolution NMR Spectroscopy for Rapid Chemical and Biological Applications in Inhomogeneous Magnetic Fields.

NMR spectroscopy is a commonly used analytical technique in practical applications, and its applicability is further promoted by pure chemical shift techniques based on spectral simplification for analyses. Unfortunately, magnetic field inhomogeneity caused by adverse experimental conditions remains an obstacle restricting NMR applications. In this study, we introduce a new NMR method for high-resolution pure shift proton (1H) NMR measurements in inhomogeneous magnetic fields. We demonstrate that the method allows one to perform chemical analyses on complex solutions in deshimmed magnetic fields, to obtain metabolite information on intact biological tissues with intrinsic field inhomogeneities and to achieve in situ electrochemical detection under externally adverse field conditions. This approach is readily implemented on common commercial NMR instruments without field shimming and locking procedures, specialized hardware requirements as well as complicated sample pretreatments. It provides an effective tool for NMR applications to high-resolution chemical and biological measurements under inhomogeneous magnetic field conditions.

Ultrahigh-resolution spectroscopy for methyl mercaptan at the ν2-band by a distributed feedback interband cascade laser

The ultrahigh-resolution mid-infrared absorption spectrum of methyl mercaptan (CH3SH) was recorded and analyzed in the region of 2945–2953cm-1, where the strong ν2-band is located. Benefitting from the high-resolution of tunable laser absorption spectrometry (TLAS) with a distributed feedback interband cascade laser (DFB-ICL), 12-strong and 27-weak air-broadened absorption peaks belonging to the ν2-band of CH3SH were assigned with resolution of better than 2.24×10-5cm-1(~26fm/670kHz) and absorption cross section precision of 2.0%, at temperature of 298.15K and pressure of 1atm. For further description of the assigned transitions, the spectral line parameters and cross sections of these absorption peaks versus pressure were investigated. These ultrahigh resolution air-broadened spectra can be used as reference data for CH3SH remote sensing and absolute spectral measurement applications.

A spectromicroscope for nanophysics

The new generation of spectromicroscopes opens up new fields of nanophysics. Beyond the impressive spatial and spectral resolutions delivered by these new instruments - an obvious example being the Hermes machine conceived, designed and built by O. L. Krivanek, who is honoured in this journal issue - here we wish to address the motivations and conditions required to get the best out of them. We first coarsely sketch the panorama of physical excitations worth motivating the use of ultra-high resolution spectroscopy techniques in STEMs. We then give general considerations on the use of combined spectroscopy techniques, reciprocal space measurements and additional time-resolved experiments to complement the wealth of the physical insights provided by the new-generation spectromicroscopes. We then comment on the newly enhanced mechanical and high voltage stabilities and their effects on the accuracy of spectroscopic measurements. The use of temperature-dependent experiments, to bring electron spectroscopy techniques to the standard of other condensed matter physics techniques such as optical and X-ray spectroscopy, is also described. We finish by evaluating the impact of other breakthrough developments, such as energy gain electron spectroscopy or electron-phase manipulation, on the use of ultra-high resolution spectromicroscopes.

Gareth A. Morris

Angewandte Chemie International EditionVolume 56, Issue 27 p. 7710-7710 Author ProfileFree Access Gareth A. Morris First published: 01 March 2017 https://doi.org/10.1002/anie.201701095AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “I advise my students to ignore my advice. They usually do. My favorite way to spend a holiday is walking on the Northumberland coast ...” This and more about Gareth A. Morris can be found on page 7710. Gareth A. Morris The author presented on this page has recently published his 10th article in Angewandte Chemie in 10 years: “Ultrahigh-Resolution Diffusion-Ordered Spectroscopy”: M. Foroozandeh, L. Castañar, L. G. Martins, D. Sinnaeve, G. D. Poggetto, C. F. Tormena, R. W. Adams, G. A. Morris, M. Nilsson, Angew. Chem. Int. Ed. 2016, 55, 15579; Angew. Chem. 2016, 128, 15808. Date of birth: July 1954 Position: Professor of Physical Chemistry, University of Manchester E-mail: g.a.morris@manchester.ac.uk Homepage: http://www.chemistry.manchester.ac.uk/people/staff/profile/?ea=Gareth.Morris ORCID: 0000-0002-4859-6259 Education: 1976 MA in Natural Sciences (Chemistry), University of Oxford 1978 DPhil (supervised by Ray Freeman), University of Oxford 1978–1981 Fellow by Examination, Magdalen College, University of Oxford 1978–1979 (on leave of absence from Oxford), Izaak Walton Killam Postdoctoral Fellow with Laurie Hall, University of British Columbia Awards: 2001 Royal Society of Chemistry Award in Magnetic Resonance Spectroscopy; 2011 Russell Varian Prize, EUROMAR Magnetic Resonance Meeting; 2014 elected Fellow of the Royal Society; 2015 James N. Shoolery Award, SMASH Small Molecule NMR Conference Current research interests: Development and application of new techniques in high-resolution NMR spectroscopy, including pure shift NMR, DOSY, and broadband methods Hobbies: Music, reading, walking, growing vegetables I advise my students to ignore my advice. They usually do. My favorite way to spend a holiday is walking on the Northumberland coast. My first experiment was probably something out of the Ladybird book Magnets, Bulbs and Batteries when I was aged around 7. Nowadays I just have bigger magnets to play with. My favorite quote changes by the hour, but I quite like Hofstadter's First Law: It always takes longer than you think, even when you take into account Hofstadter's First Law. The secret of being a successful scientist is luck. Being a good scientist, though, is more complicated … My favorite NMR pulse sequence is the spin echo: simple, counterintuitive, and endlessly adaptable, it is used right across science from magnetic resonance imaging to NMR crystallography. My science “heroes” are the pioneers of NMR, such as Felix Bloch and Erwin Hahn. The most important thing I learned from my students is that if you can't teach something, you don't understand it. The natural talent I would like to be gifted with is musicianship. In science, with modest abilities and a modicum of good fortune you can get a long way, but music, like mathematics, is much less forgiving. The greatest scientific advance of the last decade was the Human Genome Project. Now all we need to do is to work out what it means, both practically and philosophically. My 5 top papers: References 1“Selective excitation in Fourier transform nuclear magnetic resonance”: G. A. Morris, R. Freeman, J. Magn. Reson. 1978, 29, 433. (A detailed analysis with illustrative applications of the DANTE class of pulse sequences.) 2“Enhancement of Nuclear Magnetic Resonance Signals by Polarization Transfer”: G. A. Morris, R. Freeman, J. Am. Chem. Soc. 1979, 101, 760. (The INEPT pulse sequence.) 3“Quantitative Interpretation of Diffusion-Ordered NMR Spectra: Can We Rationalize Small Molecule Diffusion Coefficients?”: R. Evans, Z. Deng, A. K. Rogerson, A. S. McLachlan, J. J. Richards, M. Nilsson, G. A. Morris, Angew. Chem. Int. Ed. 2013, 52, 3199; Angew. Chem. 2013, 125, 3281. (An empirical but surprisingly effective approach to interpreting diffusion coefficients.) 4“Simultaneously Enhancing Spectral Resolution and Sensitivity in Heteronuclear Correlation NMR”: L. Paudel, R. W. Adams, P. Király, J. A. Aguilar, M. Foroozandeh, M. J. Cliff, M. Nilsson, P. Sándor, J. P. Waltho, G. A. Morris, Angew. Chem. Int. Ed. 2013, 52, 11616; Angew. Chem. 2013, 125, 11830. (Simultaneously improves both the resolving power and the signal-to-noise ratio of an NMR experiment.) 5“Ultrahigh-Resolution NMR Spectroscopy”: M. Foroozandeh, R. W. Adams, N. Meharry, D. Jeannerat, M. Nilsson, G. A. Morris, Angew. Chem. Int. Ed. 2014, 53, 6990; Angew. Chem. 2014, 126, 7110. (The PSYCHE method for pure shift NMR spectroscopy, which offers substantially improved sensitivity over previous techniques.) Volume56, Issue27June 26, 2017Pages 7710-7710 ReferencesRelatedInformation

Frequency-Comb Spectrum of Periodic-Patterned Signals.

Using arbitrary periodic pulse patterns we show the enhancement of specific frequencies in a frequency comb. The envelope of a regular frequency comb originates from equally spaced, identical pulses and mimics the single pulse spectrum. We investigated spectra originating from the periodic emission of pulse trains with gaps and individual pulse heights, which are commonly observed, for example, at high-repetition-rate free electron lasers, high power lasers, and synchrotrons. The ANKA synchrotron light source was filled with defined patterns of short electron bunches generating coherent synchrotron radiation in the terahertz range. We resolved the intensities of the frequency comb around 0.258THz using the heterodyne mixing spectroscopy with a resolution of down to 1Hz and provide a comprehensive theoretical description. Adjusting the electron's revolution frequency, a gapless spectrum can be recorded, improving the resolution by up to 7 and 5 orders of magnitude compared to FTIR and recent heterodyne measurements, respectively. The results imply avenues to optimize and increase the signal-to-noise ratio of specific frequencies in the emitted synchrotron radiation spectrum to enable novel ultrahigh resolution spectroscopy and metrology applications from the terahertz to the x-ray region.

ESSENSE: Ultra high resolution spectroscopy for the ESS

The instrument concept for a very high intensity neutron spin-echo spectrometer with ultimate resolution properties has been developed and submitted as an instrument proposal to ESS. Effective intensity gain factors up to 30 compared to the best current instruments are anticipated. In addition the resolution will be boosted to the technical limits by newly designed superconducting precession solenoids. The intensity gain results from the use of an optimized guide transporting the high flux from the ESS cold moderator on the one side and from the utilization of an extended wavelength frame of 8 Å yielding a multiplication of information collection rate on the other side. The instrument thus enables novel views on soft matter systems ranging from polymers, functional gels and more to to dynamics of biological molecules with relevance for MD development; the employment of new techniques for surface NSE (GINSE) may contribute to new knowledge in tribology and lubrication and other surface phenomena that currently are hampered by low intensity. New developments in “intelligent” polymers as e.g. self-healing, the properties of which depend on molecular mobility and dynamics, require observation at many 100 ns of correlation times with high intensity, which can be made with ESSENSE.