The hydrogen secondary ion emission yield was measured for the impact of 2.0 MeV nitrogen ions on thin LiF targets using a time of flight mass spectrometer in a coincidence setup. The sample temperature was varied from 20°C up to 150°C using a resistor facing the target holder and the incident ion charge varied between 1+ and 5+. The H+ relative yield measured was fitted to isothermal function allowing the determination of the adsorption heat for the hydrogen and other contaminant molecules adsorbed on the LiF target surface. The secondary H+ emission process was described assuming the contribution of two different mechanisms namely potential and kinetic mechanisms and the results were discussed taking into account existing models for this ion emission process.