Abstract:

　　Plasmonic tips can be used to effectively confine light on the Å scale, surpassing the diffraction limit by more than three orders of magnitude, and setting a new record in spatial resolution of optical microscopy. This is put to use in tip-enhanced Raman spectromicroscopy (TER-sm), which allows the imaging of dynamical state. Seeing an atom with chemical selectivity, the vibration of a single chemical bond within a normal mode of one molecule, seeing sound and atom resolved imaging of phonons and charge density waves are among the recent observations made in our laboratory.  I will use these examples to expand on the unusual properties and multiple facets of atomistically confined light: As light, the momentum uncertainty associated with confinement gives visible photons the wavelength of x-rays. As fields, the dramatic enhancement allows detection of the feeble Raman effect from individual molecules. As photons, only two Fock states can be trapped on the tip imposing strict photonics. And in the imposed quantum tunneling limit of plasmons, field and current of the confined electrons provides a more natural description of the light-matter interaction and associated observables. There is rich photophysics to be harnessed at plasmonic nanojunctions, with already demonstrated applications in single molecule devices and electronics.

Biosketch:

　　V. Ara Apkarian is a Distinguished Professor of Chemical Physics at UCI and Director of the NSF Center for Chemical Innovation on Chemistry at the Space-Time Limit (2007-present). He holds BS and PhD degrees in Chemistry from USC and Northwestern. Following a postdoctoral fellowship at Cornell, he joined the Chemistry faculty at UCI in 1983, where he has served as Department Chair (2004-2007) and as the founding co-Director of the Chemical and Materials Physics (ChaMP) program.

　　Apkarian is a Foreign Member of the National Academy of Sciences of Armenia, a Fellow of APS, AAAS and SPIE, and has been recognized with awards in teaching, service and research, including the Dreyfus Award (1983), Sloan Fellowship (1990), Humboldt Prize (1996), UCI Distinguished Faculty Award for Teaching (2006), USC Distinguished Alumnus Award (2007), Charles Bennett Award for service (2008), the ACS Award in Experimental Physical Chemistry (2014), and an Honorary Doctorate from the University of Jyväskylä, Finland (2016).

　　His principle scientific contributions are in photophysics, ultrafast molecular and quantum dynamics in condensed matter, nonlinear optics, spectroscopy, and atomistic spectromicroscopy. His work, which combines experiment and theory on a range of topics, has appeared in ~200 peer-reviewed publications. He has organized/co-organized more than 30 scientific conferences and workshops in topics ranging from photophysics, low temperature chemistry and physics, condensed phase photodynamics, ultrafast processes, superfluid helium, molecular videography, and chemistry at the space-time limit. His current research combines ultrafast nonlinear optics and plasmonics with scanning-probe microscopy to interrogate dynamics of single molecules and extended states of matter with atomistic resolution.