  We have carried out the first comprehensive investigation of enhanced line
emission from molecular hydrogen, H$_{2}$ at 1333.79 {\AA}, observed at flare
ribbons in SOL2014-04-18T13:03. The cool H$_{2}$ emission is known to be
fluorescently excited by Si IV 1402.77 {\AA} UV radiation and provides a unique
view of the temperature minimum region (TMR). Strong H$_{2}$ emission was
observed when the Si IV 1402.77 {\AA} emission was bright during the flare
impulsive phase and gradual decay phase, but it dimmed during the GOES peak.
H$_{2}$ line broadening showed non-thermal speeds in the range 7-18
$\rm{km~s}^{-1}$, possibly corresponding to turbulent plasma flows. Small red
(blue) shifts, up to 1.8 (4.9) $\rm{km~s}^{-1}$ were measured. The intensity
ratio of Si IV 1393.76 {\AA} and Si IV 1402.77 {\AA} confirmed that plasma was
optically thin to Si IV (where the ratio = 2) during the impulsive phase of the
flare in locations where strong H$_{2}$ emission was observed. In contrast, the
ratio differs from optically thin value of 2 in parts of ribbons, indicating a
role for opacity effects. A strong spatial and temporal correlation between
H$_{2}$ and Si IV emission was evident supporting the notion that fluorescent
excitation is responsible.
