RICHARD BERNSTEIN LECTURE

When
Mon, May 15 4:00pm to 7:00pm
Where
2033 Young Hall
Speaker Prof. Brook H. Pate
Hosted by
Dept. of Chemistry and Biochemistry, UCLA
310-206-6924
Description

"Clusters, Complexes, and Chirality: Pulsed Jet Rotational Spectroscopy in Physical and Analytical Chemistry"

Abstract: Recent advances in high-speed digital electronics have made it possible to develop broadband instruments for Fourier transform molecular rotational spectroscopy using chirped-pulse excitation of the sample.  These techniques have reduced measurement times for rotational spectroscopy by about a factor of 1000 over the previous technology.  They have also made it possible to design high-sensitivity instruments that operate at low frequency where the peak transition strengths occur for larger molecules and clusters.[1]  The application of chirped-pulse spectroscopy to the structure and dynamics of water clusters will be presented.  The high-resolution of molecular beam rotational spectroscopy makes it possible to study complex chemical mixtures and this feature is required to perform structure determination of the large number of water clusters produced in the pulsed jet.[2]  In some cases, the spectra show tunneling effects that have revealed concerted tunneling processes in the water clusters.[3]  Our current research emphasis is the development of analytical chemistry techniques using pulsed jet spectroscopy to solve the challenging problem of chiral analysis of molecules with multiple chiral centers.  This emphasis follows a major advance in the field of rotational chemistry from Patterson, Schnell, and Doyle that demonstrated the ability to perform high-sensitivity chiral three-wave mixing rotational spectroscopy.[4]  This approach has recently been augmented with a chiral tag methodology similar to the use of chiral resolving agents in NMR spectroscopy.  The current status of these methods for determining the absolute configuration of molecules and making quantitative measurements of the enantiomeric excess will be presented.

[1] Cristóbal Pérez, Simon Lobsiger, Nathan A. Seifert, Daniel P. Zaleski, Berhane Temelso, George C. Shields, Zbigniew Kisiel,  and Brooks H. Pate, “Broadband Fourier Transform Rotational Spectroscopy for Structure Determination: The Water Heptamer (Frontiers Article)”, Chem. Phys. Lett. 571, 1-15 (2013).

[2] Cristóbal Pérez, Matt T. Muckle, Daniel P. Zaleski, Nathan A. Seifert, Berhane Temelso, George C. Shields, Zbigniew Kisiel, and Brooks H. Pate, “Structures of Cage, Prism, and Book Isomers of Water Hexamer from Broadband Rotational Spectroscopy”, Science 336, 897-901 (2012).

[3] Jeremy O. Richardson, Cristóbal Pérez, Simon Lobsiger, Adam A. Reid, Berhane Temelso, George C. Shields, Zbigniew Kisiel, David J. Wales, Brooks H. Pate, and Stuart C. Althorpe, “Concerted hydrogen-bond breaking by quantum tunneling in the water hexamer prism”, Science 351, 1310-1313 (2016).

[4] David Patterson, Melanie Schnell, John M. Doyle, “Enantiomer-specific detection of chiral molecules via microwave spectroscopy”, Nature 497, 475 (2013).

SEMINAR

Location: 2033 Young Hall

Time: 4:00 PM

RECEPTION

Location: 3037 Young Hall

Time: 5:15 PM

Attachments