VUV pump -- infrared probe studies of molecular dissociation following state-selective photoexcitation
POSTER
Abstract
Time-resolved measurements employing light sources based on high-harmonics generation are typically performed using broad-band pulses aiming at the shortest pulse duration achievable. This inherently results in a population of a superposition of states. In contrast, we employed $\sim$ 100 fs VUV pulses with a narrow bandwidth of $\sim$ 200meV (filtered by a grating pair), to achieve state-selective excitation. We used 11$^{th}$ harmonic pump (centered at 17.3 eV) -- 800 nm probe pulse sequence to trigger the dissociative ionization of O$_{2}$ and CO$_{2}$, which was characterized by energy- and angle-resolved photoion and photoelectron detection. While for the case of O$_{2}$ the data can be understood in terms of the (net) absorption of one and two 800 nm photons from the VUV-excited ionic state, the preliminary CO$_{2}$ results manifest rich dynamics, which surprisingly resembles the behavior observed in a recent experiment [1], where a comb of 11$^{th}$ to 17$^{th}$ harmonics was used. \\[4pt] [1] H. Timmers et al, Phys. Rev. Lett. 113, 113003 (2014).
*Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Science, Office of Science, U.S. Department of Energy. K.R.P. supported by National Science Foundation Award No. IIA-1430493