Berkeley Lab

Probing aqueous carbonates with soft X-ray spectroscopy

“If you don’t have a bright mind, wear a bright shirt,” said Richard Saykally, professor of chemistry at UC Berkeley, as he walked to the podium of the Multimodal In Situ Characterization Symposium in a black and pink Hawaiian shirt. Saykally’s group uses atom specific soft X-ray spectroscopy to probe liquids and their surfaces, particularly aqueous carbonates. While it is well known that carbonate/bicarbonate and acids react to form water and carbon dioxide, the mechanism for this reaction is not known. By using a fast-flow microjet mixing system, they are able to collect spectra while changing pH to generate species of interest with a mixing time of 0.5 milliseconds (in comparison, the half-life of carbonic acid is 26 milliseconds). By combining experimental spectra with spectra predicted by David Prendergast’s group with the excited-electron core-hole approach (XCH), the hydration structure of aqueous carbonates was determined.


Moving forward, the group has started incorporating a surface sensitive spectroscopic technique, X-ray photoemission spectroscopy (XPS). While the current result, which is that both carbonate and carbonic acid are present at higher concentrations than bicarbonate, is unexpected, Saykally comments that “it’s not a sin to be wrong – it’s a sin to be boring!” The new results have yet to be fully explained, but will spur more studies in this field.


Needless to say, Saykally has a bright mind, but we still like his Hawaiian shirts.