Fully Coherent Triple Sum Frequency Spectroscopy of a Benzene Fermi Resonance BoyleErin S. PakoulevAndrei V. WrightJohn C. 2013 In this paper we present a new multiresonant coherent multidimensional spectroscopy (CMDS) technique employing a pathway that is both fully coherent and necessarily unique. This technique is based on a Triple Sum Frequency (TSF) coherence pathway with three excitation pulses having frequencies ω<sub>1</sub>, ω<sub>2</sub>, and ω<sub>3</sub> and the phase matching condition <i>k⃗</i><sub>1</sub> + <i>k⃗</i><sub>2</sub> + <i>k⃗</i><sub>3</sub>. Two-dimensional spectra are created by independently tuning the ω<sub>1</sub> and ω<sub>2</sub> pulses across vibrational resonances while monitoring the intensity of a visible output beam created by a Raman transition induced by the ω<sub>3</sub> pulse. Two-dimensional plots of the coherent dynamics are created by independently scanning the τ<sub>21</sub> and τ<sub>31</sub> delay times between the different frequency excitation pulses over all time orderings. TSF CMDS separates fundamental and overtone/combination band states uniquely onto the ω<sub>1</sub> and ω<sub>2</sub> axes when τ<sub>21</sub> ≠ 0. TSF is valuable in its ability to probe states of complementary parity to those seen in Doubly Vibrationally Enhanced Four-Wave Mixing (DOVE-FWM), the other fully coherent mixed electronic/vibrational CMDS method. This capability is demonstrated through the use of neat benzene as a model system, where the center of inversion imposes strict parity selection rules.