About

Richard J. Saykally, born in 1947, is a Professor of the Graduate School in the Department of Chemistry at the University of California, Berkeley. He holds a B.S. from the University of Wisconsin-Eau Claire (1970) and a Ph.D. from the University of Wisconsin-Madison (1977). His postdoctoral work was conducted as a National Research Council Fellow at NIST in Boulder, Colorado. Saykally's research focuses on developing new laser and synchrotron spectroscopy methods for studying chemistry in liquid systems, new forms of matter, and properties and reactions at liquid interfaces, with particular emphasis on water and aqueous systems. His active projects include X-ray spectroscopy of liquids and interfaces, nonlinear optical spectroscopy, and chemical reactions at liquid interfaces. Throughout his career, he has received numerous awards and honors, including the Dreyfus Award, the Miller Research Professor title, the E.K. Plyler Prize for Molecular Spectroscopy, and membership in the National Academy of Sciences. He is recognized for his pioneering contributions to physical chemistry, spectroscopy, and the study of liquids and interfaces.

Research topics

• Materials science
• Environmental science
• Mechanics
• Organic chemistry
• Chemical engineering
• Engineering
• Environmental chemistry
• Chemistry
• Physics

Selected publications

• The Role of the Droplet Interface in Controlling the Multiphase Oxidation of Thiosulfate by Ozone

  ChemRxiv · 2025-01-21

  preprintOpen access

  Predicting reaction kinetics in aqueous microdroplets, including aerosols and cloud droplets, is challenging due to the probability that the underlying reaction mechanism can occur both at the surface and in the interior of the droplet. Here, we use a stochastic reaction-diffusion model of thiosulfate oxidation by gas phase ozone to examine how the interface influences the multiphase reaction kinetics measured in levitated microdroplets using mass spectrometry. Building a realistic kinetic model of multiphase reactions requires both a detailed multistep reaction mechanism as well as the surface affinities of all reactants and products. Deep-UV Second Harmonic Generation spectroscopy is used to probe surface affinities of thiosulfate, sulfate, and sulfite, key species in the reaction mechanism. Thiosulfate has an appreciable surface affinity with a measured Gibbs free energy of adsorption of -7.29 ± 2.47 kJ/mol in neutral solution, while sulfate and sulfite exhibit negligible surface propensity. The Gibbs free energy is combined with data from liquid flat jet ambient pressure x-ray photoelectron spectroscopy to constrain the concentration of thiosulfate at the surface in the kinetic model. Kinetic simulations show that the primary reaction between thiosulfate and ozone occurs at the interface and in the bulk, with the contribution of the interface decreasing from ~65% at pH 5 to ~45% at pH 13. Additionally, sulfate, the major product of thiosulfate ozonation and an important species in atmospheric processes, can be produced by two different pathways at pH 5, one with a contribution from the interface of >70% and the other occurring predominantly in the bulk (>98%). Finally, we use the kinetic model to demonstrate the impact of a range of atmospherically relevant droplet sizes and reactant concentrations on product distributions and relative importance of surface and bulk chemistry. The observations in this work have implications for mining wastewater remediation and are likely applicable to other atmospherically-relevant reaction mechanisms, suggesting that future microdroplet/aerosol chemistry studies should carefully consider the role of both interfacial and bulk chemistry.

  PublisherOA PDFDOI

• Entropy or Enthalpy? Second Harmonic Generation from Liquid Sheets Reveals Different Ion Adsorption Mechanisms for Air–Water and Oil–Water Interfaces

  Journal of the American Chemical Society · 2025-08-08

  articleSenior author

  The mechanism by which ions adsorb to immiscible liquid-liquid interfaces is central to our understanding of heterogeneous aerosol chemistry, "on-water" catalysis, and biological systems. However, the microscopic details regarding ion adsorption to such interfaces have primarily come from theoretical efforts, owing to several experimental difficulties, viz., reliable preparation of experimentally accessible and contamination-free liquid-liquid interfaces and the absence of spectroscopic tools to unambiguously probe buried surfaces. To overcome these challenges and reveal vital details of ion adsorption to a prototypical hydrophobic liquid-liquid interface, we combine free-flowing planar liquid sheets with deep UV second harmonic generation spectroscopy. The micrometer-thick, layered free-flowing sheets enable the simultaneous measurement of ion adsorption to both the air-water and water-heptane interfaces, and interference of the signal between multiple interfaces permits the retrieval of valuable phase information that is normally not accessible with this technique. Specifically, we measure temperature-dependent Langmuir isotherms of the thiocyanate anion at both interfaces and disentangle the entropic and enthalpic contributions to the Gibbs free energy of adsorption. We find that anion adsorption to these two surfaces has opposite thermodynamic driving forces, with ions being stabilized at the air-water interface by a favorable enthalpy change, whereas ions are stabilized at the water-heptane interface by a favorable entropy change.

  PublisherDOI

• Surface structure of water from soft X-ray second harmonic generation

  Nature Communications · 2025-11-26 · 4 citations

  articleOpen access

  The microscopic structure of water's surface is crucial to many natural and industrial processes, but studying its hydrogen bond (H-bond) network directly remains challenging due to the required interfacial sensitivity of experimental techniques. By leveraging advances in flat liquid sheet microjets and terawatt-scale attosecond soft X-ray pulses from the LCLS X-ray free electron laser, we employed soft X-ray second harmonic generation (SXSHG) spectroscopy to examine the liquid water/vapor interface. SXSHG combines the elemental selectivity of X-ray spectroscopies with the surface selectivity of SHG and gives access to the electronic structure of interfacial species. Here, we show the SXSHG spectrum differs from bulk water's X-ray absorption, with its peak shifted several eV, indicating a vastly different electronic environment at the interface as compared to the bulk. First-principles electronic structure calculations show the signal is highly sensitive to H-bond interactions, such as water molecules accepting a single H-bond, which are surface abundant.

  PublisherOA PDFDOI

• Hydrogen bond breaking dynamics in water clusters: Terahertz VRT spectroscopy of the 20 μm out-of-plane libration

  2025-08-17

  article1st authorCorresponding

  THE out-of-plane librational band is the most prominent feature in the intermolecular vibrational spectrum of bulk water, and has vital consequences for hydrogen bond dynamics. Excitation of this vibration, which occurs in the 500-800 cm 1 region, has been shown to comprise motions that break and reform hydrogen bonds, and the hydrogen bond breaking process has been shown to be highly local, and largely unaffected by hydrogen bond order. Thus, water clusters present a convenient route for examining details of these hydrogen bond dynamics. Additionally, analysis of the many-body expansion of the water-water interaction potential has shown that the most significant terms are the 2 and 3 body terms, which comprise ∼99% of the interaction energy. Towards the development of improved water models, terahertz vibration-rotation-tunneling (VRT) experiments on water clusters have been shown to accurately probe the short-range interactions. The key distinctions between water clusters and the bulk are the free hydrogens of the clusters. These hydrogens are predicted to have little effect on the librational motions, as evidenced by low-resolution spectroscopy studies of small clusters (n = 10-100). Here we report the high-resolution terahertz VRT spectra of a librational vibration near 15 THz for the water dimer, trimer, pentamer, and hexamer, measured with a far-IR lead-salt diode laser spectrometer employing supersonic beam production of water clusters.

  PublisherDOI

• The role of the droplet interface in controlling the multiphase oxidation of thiosulfate by ozone

  Chemical Science · 2025-01-01 · 3 citations

  articleOpen access

  in neutral solution, while sulfate and sulfite exhibit negligible surface propensity. The Gibbs free energy is combined with data from liquid flat jet ambient pressure X-ray photoelectron spectroscopy to constrain the concentration of thiosulfate at the surface in our model. Stochastic kinetic simulations leveraging these novel measurements show that the primary reaction between thiosulfate and ozone occurs at the interface and in the bulk, with the contribution of the interface decreasing from ∼65% at pH 5 to ∼45% at pH 13. Additionally, sulfate, the major product of thiosulfate ozonation and an important species in atmospheric processes, can be produced by two different pathways at pH 5, one with a contribution from the interface of >70% and the other occurring predominantly in the bulk (>98%). The observations in this work have implications for mining wastewater remediation, atmospheric chemistry, and understanding other complex reaction mechanisms in multiphase environments. Future interfacial or microdroplet/aerosol chemistry studies should carefully consider the role of both surface and bulk chemistry.

  PublisherOA PDFDOI

• Autobiography of Richard J. Saykally

  The Journal of Physical Chemistry A · 2025-01-23

  article1st authorCorresponding
  PublisherDOI

• Strong adsorption of guanidinium cations to the air–water interface

  Proceedings of the National Academy of Sciences · 2025-01-10 · 6 citations

  articleOpen accessSenior authorCorresponding

  Combining Deep-UV second harmonic generation spectroscopy with molecular simulations, we confirm and quantify the specific adsorption of guanidinium cations to the air-water interface. Using a Langmuir analysis of measurements at multiple concentrations, we extract the Gibbs free energy of adsorption, finding it larger than typical thermal energies. Molecular simulations clarify the role of polarizability in tuning the thermodynamics of adsorption, and establish the preferential parallel alignment of guanidinium at the air-water interface. As a polyatomic cation, guanidinium represents one of the few examples of a positively charged species to exhibit a propensity for the air-water interface. As such, these results expand on the growing body of work on specific ion adsorption.

  PublisherDOI

• A Detailed Reaction Mechanism for Thiosulfate Oxidation by Ozone in Aqueous Environments

  Environmental Science & Technology · 2024-10-08 · 7 citations

  articleOpen access

  The ozone oxidation, or ozonation, of thiosulfate is an important reaction for wastewater processing, where it is used for remediation of mining effluents, and for studying aerosol chemistry, where its fast reaction rate makes it an excellent model reaction. Although thiosulfate ozonation has been studied since the 1950s, challenges remain in developing a realistic reaction mechanism that can satisfactorily account for all observed products with a sequence of elementary reaction steps. Here, we present novel measurements using trapped microdroplets to study the pH-dependent thiosulfate ozonation kinetics. We detect known products and intermediates, including SO32–, SO42–, S3O62–, and S4O62–, establishing agreement with the literature. However, we identify S2O42– as a new reaction intermediate and find that the currently accepted mechanism does not directly explain observed pH effects. Thus, we develop a new mechanism, which incorporates S2O42– as an intermediate and uses elementary steps to explain the pH dependence of thiosulfate ozonation. The proposed mechanism is tested using a kinetic model benchmarked to the experiments presented here, then compared to literature data. We demonstrate good agreement between the proposed thiosulfate ozonation mechanism and experiments, suggesting that the insights in this paper can be leveraged in wastewater treatment and in understanding potential climate impacts.

  PublisherOA PDFDOI

• Ice interfaces: general discussion

  Faraday Discussions · 2024-01-01

  article

  Paul Ryan opened the discussion of the introductory Spiers Memorial Lecture by Richard J. Saykally by communicating: You mentioned the importance of contaminants. In this case are your spectroscopy measurements done under ambient conditions where contaminants are known to play a significant rol

  PublisherDOI

• A Detailed Reaction Mechanism for Thiosulfate Oxidation by Ozone in Aqueous Environments

  ChemRxiv · 2024-09-20

  preprint

  The ozone oxidation, or ozonation, of thiosulfate is an important reaction for wastewater processing, where it is used for remediation of mining effluents, and for studying aerosol chemistry, where its fast reaction rate makes it an excellent model reaction. Although thiosulfate ozonation has been studied since the 1950’s, challenges remain in developing a realistic reaction mechanism that can satisfactorily account for all observed products with a sequence of elementary reaction steps. Here, we present novel measurements using trapped microdroplets to study the pH-dependent thiosulfate ozonation kinetics. We detect known products and intermediates, including SO32-, SO42-, S3O62-, and S4O62-, establishing agreement with the literature. However, we identify S2O42- as a new reaction intermediate, and find that the currently accepted mechanism does not directly explain observed pH effects. Thus, we develop a new mechanism, which incorporates S2O42- as an intermediate and uses elementary steps to explain the pH-dependence of thiosulfate ozonation. The proposed mechanism is tested using a kinetic model benchmarked to the experiments presented here, then compared to literature data. We demonstrate good agreement between the proposed thiosulfate ozonation mechanism and experiments, suggesting that the insights in this paper can be leveraged in wastewater treatment and in understanding potential climate impacts.

  PublisherDOI

Recent grants

• Laser Spectroscopy of Ions and Clusters

  NSF · $617k · 2010–2013

• Laser Spectroscopy of Ions and Clusters

  NSF · $570k · 2007–2011

• Laser Spectroscopy of Ions and Clusters

  NSF · $568k · 2013–2017

Frequent coauthors

• R. C. Cohen

  University of California, Berkeley

  119 shared

• Craig P. Schwartz

  University of Nevada, Las Vegas

  87 shared

• Royce K. Lam

  Lawrence Berkeley National Laboratory

  73 shared

• Kevin R. Wilson

  Lawrence Berkeley National Laboratory

  65 shared

• Walter S. Drisdell

  Lawrence Berkeley National Laboratory

  65 shared

• Christopher D. Cappa

  University of California, Davis

  62 shared

• Anthony M. Rizzuto

  Lawrence Berkeley National Laboratory

  59 shared

• Andrew M. Duffin

  Pacific Northwest National Laboratory

  59 shared

Awards & honors

• Dreyfus Award (1979)
• Presidential Young Investigator Award (1984)
• E.K. Plyler Prize for Molecular Spectroscopy (1989)
• Michelson Prize for Spectroscopy (1989)
• Lippincott Medal for Spectroscopy (1992)