Seminar Physics - chemistry seminar

Speaker:

Robert E. Continetti

University of California

Title:

"Additional Perspectives: Spectroscopy of Cold Anions and Trapped Aerosols"

Abstract:

In this presentation, two additional diverse examples of the work going on in San Diego will be reviewed: the photoelectron spectroscopy of cold molecular anions produced in a cryogenic octupole accumulator trap (COAT) and the characterization of liquid and solid aerosols in a variable temperature electrodynamic balance using Mie, Fluorescence and Raman spectroscopies using the mobile quadrupole ion trap (MOBQIT).

The most recent addition to the photoelectron-photofragment coincidence (PPC) spectrometer presented last week is the ability to trap, accumulate and buffer-gas cool molecular anions prior to injection into the electrostatic ion beam trap (EIBT). The efficacy of this technique has been demonstrated by studying the competing photodetachment, ionic photodissociation and autodetachment processes that ozonide, O₃¯, exhibits at a photon energy of 3.2 eV. Using COAT to cool the anions at this photon energy allows the elimination of a dominant photodissociation/autodetachment pathway through the removal of a non-Boltzmann population of high frequency vibrational modes. No evidence for re-heating of these modes in the trapped anions on the 100 ms timescale in the EIBT has been observed.

The second part of the talk will present the MOBQIT device and illustrate real-time control and measurements of particle size using Mie scattering, size and concentration dependent effects in the fluorescence of organic dyes in aqueous, and Raman spectra of droplets doped with ammonium nitrate. Applications to studying phase changes of model sea salt aerosol systems will be discussed.

Please bring your own coffee or tea