Two-Photon Absorption (2PA) Spectroscopy

      

Two-photon absorption (2PA) spectroscopy measures the wavelength-dependent cross-sections for simultaneously absorbing two photons that are individually non-resonant with the electronic transitions of a molecule. We measure the continuous 2PA spectrum using the pump-probe technique with intense, tunable pump pulses and broadband probe pulses. When the pump and probe pulses overlap in space and time, the attenuation of probe light is proportional to the 2PA cross-section at the total energy of the two photons. Unlike other 2PA techniques, we measure the full spectrum simultaneously. 

The unit for 2PA cross-sections is called a Goeppert-Mayer (1 GM = 10-50 cm4 s molecules-1 photons-1). 

Two-photon absorption transitions can also be used to excite molecules in a two-photon pump-probe experiment. In this case, two photons are simultaneously absorbed​ from the intense pump beam to promote the molecule to an excited state. Due to the different symmetry-selection rules for one- versus two-photon excitation​, it is sometimes possible to access different excited states using the two methods.

 


Elles Group Highlights
  • Chris Otolski, Matt Barclay, and Emmaline Lorenzo all take home awards from the departmental spring honors banquet for their outstanding work. Great job!
  • Matt Barclay passes his comprehensive oral exam. Nice work, Matt!
  • Our 2PA papers with Anna Krylov highlighting Amanda's 2PA measurements are published in JCP. (Click here and here.)
  • Sadegh and Emmaline present posters at the ACS Meeting in San Francisco.
  • Emmaline is awarded an Honorable Mention for the prestigious Goldwater Scholarship. Congrats!
  • Chris Otolski successfully completed his comprehensive oral exam. Nice work, Chris!
  • Read more by clicking here...
Funding Sources