  Understanding and controlling the flow of heat is a major challenge in
nanoelectronics. When a junction is driven out of equilibrium by light or the
flow of electric charge, the vibrational and electronic degrees of freedom are,
in general, no longer described by a single temperature[1-6]. Moreover,
characterizing the steady-state vibrational and electronic distributions {\it
in situ} is extremely challenging. Here we show that surface-enhanced Raman
emission may be used to determine the effective temperatures for both the
vibrational modes and the flowing electrons in a biased metallic nanoscale
junction decorated with molecules[7]. Molecular vibrations show mode-specific
pumping by both optical excitation[8] and dc current[9], with effective
temperatures exceeding several hundred Kelvin. AntiStokes electronic Raman
emission\cite[10,11] indicates electronic effective temperature also increases
to as much as three times its no-current values at bias voltages of a few
hundred mV. While the precise effective temperatures are model-dependent, the
trends as a function of bias conditions are robust, and allow direct
comparisons with theories of nanoscale heating.
