A method for extracting the site-specific probabilities of hydrogen-rich fragment formation from the double-ionization of ethanol

Using COLTRIMS experiments examining seven different deuterium-tagged isotopologues of ethanol under the same laser pulse conditions (800 nm, 3.0×10¹⁴ W/cm², 23 fs FWHM), we measure the relative probabilities of producing H₃⁺, CH₄⁺, H₂O⁺, and H₃O⁺ as a function of the initial sites of the hydrogen atoms that compose the final products. Once the yields of the two- and three-body double ionization channels are determined for all isotopologues, the data is used to fit an overcomplete system of equations that describe the sites that may contribute to a measured final coincidence channel. To estimate the uncertainty of these site-specific probabilities, we repeatedly fit, in a Monte-Carlo fashion, a set of branching ratios randomly picked from the normal distribution associated with the measured values and their estimated error. Other related site-specific dynamic quantities, such as the kinetic energy release, can be obtained using this method.