Liquid Carbon, Glassy Carbon, and Their Surfaces

We seek to advance our fundamental understanding of the liquid state and the phase diagram of carbon by performing detailed nonlinear optical electronic and vibrational spectroscopy studies of both the bulk and the surface of liquid carbon, and to exploit our novel laser technology to explore the nature of the newly-discovered Q-carbon form. The liquid will be prepared by non-thermal melting of graphite targets with both femtosecond and nanosecond lasers. The vibrational and electronic structures of the bulk liquid will be probed as a function of delay time from the melting pulse (and thus as a function of temperature and pressure) with our recently developed chirped femtosecond coherent anti-Stokes Raman spectroscopy (c-CARS) technique. Our new broadband deep-UV electronic sum frequency generation (DUV-ESFG) spectroscopy technique will be used to probe the surfaces. Our Single Photon InfraRed Emission Spectroscopy (SPIRES) spectrometer will be used to monitor the evolution of the "super-undercooled" liquid carbon into the Q-carbon stages. This collection of experiments, interpreted with state of the art theoretical calculations performed in collaboration with Berkeley-area theorists, will characterize the structure, bonding, and dynamics of liquid carbon, Q-carbon, and the various diamond structures (needles, nano/microdiamonds, ...) nucleated from Q-carbon. Time resolved experiments will address the nucleation mechanisms of carbon nanotubes and diamond structures from the liquid and Q-carbon forms. Addition of dopants(e.g. N, B) to the diamond nano/micro-structures will be explored. The combined theoretical and experimental information obtained will ultimately be used to construct improved potential models that can describe all known phases and properties of carbon.