Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems
Abstract
Ultrafast spectroscopy and imaging have become tools utilized by a broad range of scientists involved in materials, energy, biological, and chemical sciences. Commercialization of ultrafast spectrometers including transient absorption spectrometers, vibrational sum frequency generation spectrometers, and even multidimensional spectrometers have put these advanced spectroscopy measurements into the hands of practitioners originally outside the field of ultrafast spectroscopy. There is now a technology shift occurring in ultrafast spectroscopy, made possible by new Yb-based lasers, that is opening exciting new experiments in the chemical and physical sciences. Amplified Yb-based lasers are not only more compact and efficient than their predecessors but also, most importantly, operate at many times the repetition rate with improved noise characteristics in comparison to the previous generation of Ti:sapphire amplifier technologies. Taken together, these attributes are enabling new experiments, generating improvements to long-standing techniques, and affording the transformation of spectroscopies to microscopies. This Account aims to show that the shift to 100 kHz lasers is a transformative step in nonlinear spectroscopy and imaging, much like the dramatic expansion that occurred with the commercialization of Ti:sapphire laser systems in the 1990s. The impact of this technology will be felt across a great swath of scientific communities. We first describemore »
- Authors:
-
- Central Laser Facility, Research Complex at Harwell, STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, United Kingdom
- PhaseTech Spectroscopy, Inc., 4916 East Broadway, Suite 125, Madison, Wisconsin 53716, United States
- Colorado State University, Department of Chemistry, 200 W. Lake Street, Fort Collins, Colorado 80523, United States
- University of Wisconsin, Department of Chemistry, Room 8361, 1101 University Ave., Madison, Wisconsin 53706, United States
- University of Zurich, Department of Chemistry, Winterthurerstrasse 190, Zurich CH-8057, Switzerland
- Publication Date:
- Research Org.:
- Colorado State Univ., Fort Collins, CO (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 2282655
- Alternate Identifier(s):
- OSTI ID: 2311846
- Grant/Contract Number:
- SC0016137
- Resource Type:
- Published Article
- Journal Name:
- Accounts of Chemical Research
- Additional Journal Information:
- Journal Name: Accounts of Chemical Research Journal Volume: 56 Journal Issue: 15; Journal ID: ISSN 0001-4842
- Publisher:
- American Chemical Society
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Infrared light; Infrared spectroscopy; Lasers; Probes; Ultrafast spectroscopy
Citation Formats
Donaldson, Paul M., Greetham, Greg M., Middleton, Chris T., Luther, Bradley M., Zanni, Martin T., Hamm, Peter, and Krummel, Amber T. Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems. United States: N. p., 2023.
Web. doi:10.1021/acs.accounts.3c00152.
Donaldson, Paul M., Greetham, Greg M., Middleton, Chris T., Luther, Bradley M., Zanni, Martin T., Hamm, Peter, & Krummel, Amber T. Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems. United States. https://doi.org/10.1021/acs.accounts.3c00152
Donaldson, Paul M., Greetham, Greg M., Middleton, Chris T., Luther, Bradley M., Zanni, Martin T., Hamm, Peter, and Krummel, Amber T. Mon .
"Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems". United States. https://doi.org/10.1021/acs.accounts.3c00152.
@article{osti_2282655,
title = {Breaking Barriers in Ultrafast Spectroscopy and Imaging Using 100 kHz Amplified Yb-Laser Systems},
author = {Donaldson, Paul M. and Greetham, Greg M. and Middleton, Chris T. and Luther, Bradley M. and Zanni, Martin T. and Hamm, Peter and Krummel, Amber T.},
abstractNote = {Ultrafast spectroscopy and imaging have become tools utilized by a broad range of scientists involved in materials, energy, biological, and chemical sciences. Commercialization of ultrafast spectrometers including transient absorption spectrometers, vibrational sum frequency generation spectrometers, and even multidimensional spectrometers have put these advanced spectroscopy measurements into the hands of practitioners originally outside the field of ultrafast spectroscopy. There is now a technology shift occurring in ultrafast spectroscopy, made possible by new Yb-based lasers, that is opening exciting new experiments in the chemical and physical sciences. Amplified Yb-based lasers are not only more compact and efficient than their predecessors but also, most importantly, operate at many times the repetition rate with improved noise characteristics in comparison to the previous generation of Ti:sapphire amplifier technologies. Taken together, these attributes are enabling new experiments, generating improvements to long-standing techniques, and affording the transformation of spectroscopies to microscopies. This Account aims to show that the shift to 100 kHz lasers is a transformative step in nonlinear spectroscopy and imaging, much like the dramatic expansion that occurred with the commercialization of Ti:sapphire laser systems in the 1990s. The impact of this technology will be felt across a great swath of scientific communities. We first describe the technology landscape of amplified Yb-based laser systems used in conjunction with 100 kHz spectrometers operating with shot-to-shot pulse shaping and detection. We also identify the range of different parametric conversion and supercontinuum techniques which now provide a path to making pulses of light optimal for ultrafast spectroscopy. Second, we describe specific instances from our laboratories of how the amplified Yb-based light sources and spectrometers are transformative. For multiple probe time-resolved infrared and transient 2D IR spectroscopy, the gain in temporal span and signal-to-noise enables dynamical spectroscopy measurements from femtoseconds to seconds. These gains widen the applicability of time-resolved infrared techniques across a range of topics in photochemistry, photocatalysis, and photobiology as well as lower the technical barriers to implementation in a laboratory. For 2D visible spectroscopy and microscopy with white light, as well as 2D IR imaging, the high repetition rates of these new Yb-based light sources allow one to spatially map 2D spectra while maintaining high signal-to-noise in the data. To illustrate the gains, we provide examples of imaging applications in the study of photovoltaic materials and spectroelectrochemistry.},
doi = {10.1021/acs.accounts.3c00152},
journal = {Accounts of Chemical Research},
number = 15,
volume = 56,
place = {United States},
year = {Mon Jul 10 00:00:00 EDT 2023},
month = {Mon Jul 10 00:00:00 EDT 2023}
}
https://doi.org/10.1021/acs.accounts.3c00152
Works referenced in this record:
Sub-10-fs pulses tunable from 480 to 980 nm from a NOPA pumped by an Yb:KGW source
journal, July 2014
- Liebel, Matz; Schnedermann, Christoph; Kukura, Philipp
- Optics Letters, Vol. 39, Issue 14
Coherent two-dimensional electronic mass spectrometry
journal, June 2018
- Roeding, Sebastian; Brixner, Tobias
- Nature Communications, Vol. 9, Issue 1
Direct Observation of Reactive Intermediates by Time-Resolved Spectroscopy Unravels the Mechanism of a Radical-Induced 1,2-Metalate Rearrangement
journal, October 2021
- Lewis-Borrell, Luke; Sneha, Mahima; Clark, Ian P.
- Journal of the American Chemical Society, Vol. 143, Issue 41
Photon echoes and two dimensional spectra of the amide I band of proteins measured by femtosecond IR – Raman spectroscopy
journal, January 2020
- Donaldson, Paul. M.
- Chemical Science, Vol. 11, Issue 33
High-Throughput Two-Dimensional Infrared (2D IR) Spectroscopy Achieved by Interfacing Microfluidic Technology with a High Repetition Rate 2D IR Spectrometer
journal, November 2016
- Tracy, Kathryn M.; Barich, Michael V.; Carver, Christina L.
- The Journal of Physical Chemistry Letters, Vol. 7, Issue 23
Enabling high repetition rate nonlinear THz science with a kilowatt-class sub-100 fs laser source
journal, May 2020
- Kramer, Patrick L.; Windeler, Matthew K. R.; Mecseki, Katalin
- Optics Express, Vol. 28, Issue 11
Two-color two-dimensional Fourier transform electronic spectroscopy with a pulse-shaper
journal, January 2008
- Myers, Jeffrey A.; Lewis, Kristin L.; Tekavec, Patrick F.
- Optics Express, Vol. 16, Issue 22
Theory and phase-cycling scheme selection principles of collinear phase coherent multi-dimensional optical spectroscopy
journal, September 2008
- Tan, Howe-Siang
- The Journal of Chemical Physics, Vol. 129, Issue 12
Analysis of amyloid-like secondary structure in the Cryab-R120G knock-in mouse model of hereditary cataracts by two-dimensional infrared spectroscopy
journal, September 2021
- Alperstein, Ariel M.; Molnar, Kathleen S.; Dicke, Sidney S.
- PLOS ONE, Vol. 16, Issue 9
Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights
journal, November 2019
- Bhattacherjee, Aditi; Sneha, Mahima; Lewis-Borrell, Luke
- Nature Communications, Vol. 10, Issue 1
Long-Range Vibrational Dynamics Are Directed by Watson–Crick Base Pairing in Duplex DNA
journal, April 2016
- Hithell, Gordon; Shaw, Daniel J.; Donaldson, Paul M.
- The Journal of Physical Chemistry B, Vol. 120, Issue 17
Coherent two-dimensional photocurrent spectroscopy in a PbS quantum dot photocell
journal, December 2014
- Karki, Khadga J.; Widom, Julia R.; Seibt, Joachim
- Nature Communications, Vol. 5, Issue 1
Broadband near-field infrared spectromicroscopy using photothermal probes and synchrotron radiation
journal, January 2016
- Donaldson, Paul M.; Kelley, Chris S.; Frogley, Mark D.
- Optics Express, Vol. 24, Issue 3
Direct Observation of the Microscopic Reverse of the Ubiquitous Concerted Metalation Deprotonation Step in C–H Bond Activation Catalysis
journal, January 2021
- Hammarback, L. Anders; Aucott, Benjamin J.; Bray, Joshua T. W.
- Journal of the American Chemical Society, Vol. 143, Issue 3
500 kHz OPCPA delivering tunable sub-20 fs pulses with 15 W average power based on an all-ytterbium laser
journal, January 2015
- Puppin, Michele; Deng, Yunpei; Prochnow, Oliver
- Optics Express, Vol. 23, Issue 2
Transient 2D IR spectroscopy from micro- to milliseconds
journal, March 2021
- Hamm, Peter
- The Journal of Chemical Physics, Vol. 154, Issue 10
A 100 kHz Pulse Shaping 2D-IR Spectrometer Based on Dual Yb:KGW Amplifiers
journal, January 2018
- Donaldson, P. M.; Greetham, G. M.; Shaw, D. J.
- The Journal of Physical Chemistry A, Vol. 122, Issue 3
Watching Proteins Wiggle: Mapping Structures with Two-Dimensional Infrared Spectroscopy
journal, January 2017
- Ghosh, Ayanjeet; Ostrander, Joshua S.; Zanni, Martin T.
- Chemical Reviews, Vol. 117, Issue 16
Time-Domain Vibrational Action Spectroscopy of Cryogenically Cooled, Messenger-Tagged Ions Using Ultrafast IR Pulses
journal, November 2021
- Chen, Liangyi; Dean, Jessika L. S.; Fournier, Joseph A.
- The Journal of Physical Chemistry A, Vol. 125, Issue 47
Water vibrations have strongly mixed intra- and intermolecular character
journal, September 2013
- Ramasesha, Krupa; De Marco, Luigi; Mandal, Aritra
- Nature Chemistry, Vol. 5, Issue 11
Ytterbium solid-state lasers. The first decade
journal, November 2000
- Krupke, W. F.
- IEEE Journal of Selected Topics in Quantum Electronics, Vol. 6, Issue 6
Subpicosecond kilowatt pulses from a mode-locked cw dye laser
journal, April 1974
- Shank, C. V.; Ippen, E. P.
- Applied Physics Letters, Vol. 24, Issue 8
Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy
journal, December 2011
- Xiong, W.; Laaser, J. E.; Mehlenbacher, R. D.
- Proceedings of the National Academy of Sciences, Vol. 108, Issue 52
Impact of non-equilibrium molecular packings on singlet fission in microcrystals observed using 2D white-light microscopy
journal, December 2019
- Jones, Andrew C.; Kearns, Nicholas M.; Ho, Jia-Jung
- Nature Chemistry, Vol. 12, Issue 1
100-kHz shot-to-shot broadband data acquisition for high-repetition-rate pump–probe spectroscopy
journal, January 2014
- Kanal, Florian; Keiber, Sabine; Eck, Reiner
- Optics Express, Vol. 22, Issue 14
Residue-specific structural kinetics of proteins through the union of isotope labeling, mid-IR pulse shaping, and coherent 2D IR spectroscopy
journal, September 2010
- Middleton, Chris T.; Woys, Ann Marie; Mukherjee, Sudipta S.
- Methods, Vol. 52, Issue 1
Infrared spectroscopy reveals multi-step multi-timescale photoactivation in the photoconvertible protein archetype dronpa
journal, June 2018
- Laptenok, Sergey P.; Gil, Agnieszka A.; Hall, Christopher R.
- Nature Chemistry, Vol. 10, Issue 8
Mechanism of IAPP amyloid fibril formation involves an intermediate with a transient -sheet
journal, November 2013
- Buchanan, L. E.; Dunkelberger, E. B.; Tran, H. Q.
- Proceedings of the National Academy of Sciences, Vol. 110, Issue 48
4-W, 100-kHz, few-cycle mid-infrared source with sub-100-mrad carrier-envelope phase noise
journal, January 2017
- Thiré, Nicolas; Maksimenka, Raman; Kiss, Bálint
- Optics Express, Vol. 25, Issue 2
Thermal Annealing of Singlet Fission Microcrystals Reveals the Benefits of Charge Transfer Couplings and Slip-Stacked Packing
journal, June 2020
- Armstrong, Zachary T.; Kunz, Miriam Bohlmann; Jones, Andrew C.
- The Journal of Physical Chemistry C, Vol. 124, Issue 28
2D IR spectroscopy at 100 kHz utilizing a Mid-IR OPCPA laser source
journal, January 2016
- Luther, Bradley M.; Tracy, Kathryn M.; Gerrity, Michael
- Optics Express, Vol. 24, Issue 4
Concepts and Methods of 2D Infrared Spectroscopy
book, January 2011
- Hamm, Peter; Zanni, Martin
- Cambridge University Press
Purely absorptive three-dimensional infrared spectroscopy
journal, April 2009
- Garrett-Roe, Sean; Hamm, Peter
- The Journal of Chemical Physics, Vol. 130, Issue 16
Spatially Resolved Two-Dimensional Infrared Spectroscopy via Wide-Field Microscopy
journal, June 2016
- Ostrander, Joshua S.; Serrano, Arnaldo L.; Ghosh, Ayanjeet
- ACS Photonics, Vol. 3, Issue 7
High-energy few-cycle pulses: post-compression techniques
journal, November 2020
- Nagy, Tamas; Simon, Peter; Veisz, Laszlo
- Advances in Physics: X, Vol. 6, Issue 1
Fluorescence-detected two-dimensional electronic coherence spectroscopy by acousto-optic phase modulation
journal, December 2007
- Tekavec, Patrick F.; Lott, Geoffrey A.; Marcus, Andrew H.
- The Journal of Chemical Physics, Vol. 127, Issue 21
A 100 kHz Time-Resolved Multiple-Probe Femtosecond to Second Infrared Absorption Spectrometer
journal, February 2016
- Greetham, Gregory M.; Donaldson, Paul M.; Nation, Charlie
- Applied Spectroscopy, Vol. 70, Issue 4
Shot-to-shot 2D IR spectroscopy at 100 kHz using a Yb laser and custom-designed electronics
journal, October 2020
- Farrell, Kieran M.; Ostrander, Josh S.; Jones, Andrew C.
- Optics Express, Vol. 28, Issue 22
Sequence of Events during Peptide Unbinding from RNase S: A Complete Experimental Description
journal, May 2021
- Jankovic, Brankica; Ruf, Jeannette; Zanobini, Claudio
- The Journal of Physical Chemistry Letters, Vol. 12, Issue 21
Dual spectral phase and diffraction angle compensation of a broadband AOM 4-f pulse-shaper for ultrafast spectroscopy
journal, December 2019
- Jones, Andrew C.; Kunz, Miriam Bohlmann; Tigges-Green, Isabelle
- Optics Express, Vol. 27, Issue 26
Broadband 2D electronic spectrometer using white light and pulse shaping: noise and signal evaluation at 1 and 100 kHz
journal, January 2017
- Kearns, Nicholas M.; Mehlenbacher, Randy D.; Jones, Andrew C.
- Optics Express, Vol. 25, Issue 7
Long seed, short pump: converting Yb-doped laser radiation to multi-µJ few-cycle pulses tunable through 2.5–15 µm
journal, April 2022
- Budriūnas, Rimantas; Jurkus, Karolis; Vengris, Mikas
- Optics Express, Vol. 30, Issue 8
Time-resolved infra-red studies of photo-excited porphyrins in the presence of nucleic acids and in HeLa tumour cells: insights into binding site and electron transfer dynamics
journal, January 2022
- Keane, Páraic M.; Zehe, Clara; Poynton, Fergus E.
- Physical Chemistry Chemical Physics, Vol. 24, Issue 44
Noise analysis and noise reduction methods in kilohertz pump-probe experiments
journal, July 2007
- Anderson, Kevin E. H.; Sewall, Samuel L.; Cooney, Ryan R.
- Review of Scientific Instruments, Vol. 78, Issue 7
Three-dimensional electronic spectroscopy of excitons in GaAs quantum wells
journal, October 2009
- Turner, Daniel B.; Stone, Katherine W.; Gundogdu, Kenan
- The Journal of Chemical Physics, Vol. 131, Issue 14
Manganese-Mediated C–H Bond Activation of Fluorinated Aromatics and the ortho-Fluorine Effect: Kinetic Analysis by In Situ Infrared Spectroscopic Analysis and Time-Resolved Methods
journal, January 2022
- Hammarback, L. Anders; Bishop, Amy L.; Jordan, Christina
- ACS Catalysis, Vol. 12, Issue 2
Application of 2D IR Bioimaging: Hyperspectral Images of Formalin-Fixed Pancreatic Tissues and Observation of Slow Protein Degradation
journal, August 2021
- Dicke, Sidney S.; Alperstein, Ariel M.; Schueler, Kathryn L.
- The Journal of Physical Chemistry B, Vol. 125, Issue 33
60-fsec pulse generation from a self-mode-locked Ti:sapphire laser
journal, January 1991
- Spence, D. E.; Kean, P. N.; Sibbett, W.
- Optics Letters, Vol. 16, Issue 1
Femtosecond to microsecond observation of the photochemical reaction of 1,2-di(quinolin-2-yl)disulfide with methyl methacrylate
journal, January 2017
- Koyama, Daisuke; Donaldson, Paul M.; Orr-Ewing, Andrew J.
- Physical Chemistry Chemical Physics, Vol. 19, Issue 20
Single-stage MHz mid-IR OPA using LiGaS2and a fiber laser pump source
journal, March 2018
- Penwell, Samuel B.; Whaley-Mayda, Lukas; Tokmakoff, Andrei
- Optics Letters, Vol. 43, Issue 6
Rapid-scan coherent 2D fluorescence spectroscopy
journal, January 2017
- Draeger, Simon; Roeding, Sebastian; Brixner, Tobias
- Optics Express, Vol. 25, Issue 4
Compression of optical pulses to six femtoseconds by using cubic phase compensation
journal, January 1987
- Fork, R. L.; Brito Cruz, C. H.; Becker, P. C.
- Optics Letters, Vol. 12, Issue 7, p. 483-485
Supercontinuum-seeded few-cycle mid-infrared OPCPA system
journal, January 2016
- Rigaud, Philippe; Van de Walle, Aymeric; Hanna, Marc
- Optics Express, Vol. 24, Issue 23
Transient 2D-IR Spectroscopy: Snapshots of the Nonequilibrium Ensemble during the Picosecond Conformational Transition of a Small Peptide
journal, August 2003
- Bredenbeck, Jens; Helbing, Jan; Behrendt, Raymond
- The Journal of Physical Chemistry B, Vol. 107, Issue 33
How to turn your pump–probe instrument into a multidimensional spectrometer: 2D IR and Vis spectroscopiesvia pulse shaping
journal, January 2009
- Shim, Sang-Hee; Zanni, Martin T.
- Phys. Chem. Chem. Phys., Vol. 11, Issue 5
Short-Range Catalyst–Surface Interactions Revealed by Heterodyne Two-Dimensional Sum Frequency Generation Spectroscopy
journal, October 2015
- Wang, Jiaxi; Clark, Melissa L.; Li, Yingmin
- The Journal of Physical Chemistry Letters, Vol. 6, Issue 21
Ultrafast vibrational dynamics of water at a charged interface revealed by two-dimensional heterodyne-detected vibrational sum frequency generation
journal, September 2012
- Singh, Prashant Chandra
- The Journal of Chemical Physics, Vol. 137, Issue 9
Ultrafast 2D IR microscopy
journal, January 2014
- Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei
- Optics Express, Vol. 22, Issue 15
Pentacarbonylchromium-solvent complexes
journal, April 1974
- Kelly, John M.; Bent, David V.; Hermann, Horst
- Journal of Organometallic Chemistry, Vol. 69, Issue 2
Heterodyned 3D IR spectroscopy
journal, November 2007
- Ding, Feng; Zanni, Martin T.
- Chemical Physics, Vol. 341, Issue 1-3
Purely absorptive fifth-order three-dimensional electronic spectroscopy
journal, December 2012
- Zhang, Zhengyang; Wells, Kym Lewis; Tan, Howe-Siang
- Optics Letters, Vol. 37, Issue 24
Femtochemistry: Atomic-Scale Dynamics of the Chemical Bond †
journal, June 2000
- Zewail, Ahmed H.
- The Journal of Physical Chemistry A, Vol. 104, Issue 24
A stop-flow sample delivery system for transient spectroscopy
journal, December 2021
- Buhrke, David; Ruf, Jeannette; Heckmeier, Philipp
- Review of Scientific Instruments, Vol. 92, Issue 12
The molecular mechanism of light-induced bond formation and breakage in the cyanobacteriochrome TePixJ
journal, January 2023
- Ruf, Jeannette; Bindschedler, Flavia; Buhrke, David
- Physical Chemistry Chemical Physics, Vol. 25, Issue 8
Multidimensional Spectroscopy on the Microscale: Development of a Multimodal Imaging System Incorporating 2D White-Light Spectroscopy, Broadband Transient Absorption, and Atomic Force Microscopy
journal, November 2019
- Jones, Andrew C.; Kearns, Nicholas M.; Bohlmann Kunz, Miriam
- The Journal of Physical Chemistry A, Vol. 123, Issue 50
Transient 2D IR spectroscopy and multiscale simulations reveal vibrational couplings in the Cyanobacteriochrome Slr1393-g3
preprint, January 2023
- Buhrke, David; Lahav, Yigal; Rao, Aditya
- arXiv
Compression of amplified chirped optical pulses
journal, October 1985
- Strickland, Donna; Mourou, Gerard
- Optics Communications, Vol. 55, Issue 6, p. 447-449
Amplification of mid-IR continuum for broadband 2D IR spectroscopy
journal, February 2023
- Hack, John H.; Lewis, Nicholas H. C.; Carpenter, William B.
- Optics Letters, Vol. 48, Issue 4
Multidimensional Electronic Spectroscopy of Photochemical Reactions
journal, August 2015
- Nuernberger, Patrick; Ruetzel, Stefan; Brixner, Tobias
- Angewandte Chemie International Edition, Vol. 54, Issue 39
2D Electronic Spectroscopic Techniques for Quantum Technology Applications
journal, June 2021
- Collini, Elisabetta
- The Journal of Physical Chemistry C, Vol. 125, Issue 24
Observation of optical coherence in a disordered metal-molecule interface by coherent optical two-dimensional photoelectron spectroscopy
journal, May 2022
- Aeschlimann, Martin; Brixner, Tobias; Cinchetti, Mirko
- Physical Review B, Vol. 105, Issue 20