Fragmentation of thymidine induced by ultraviolet photoionization and thermal degradation

• The main fragments after photoionization are deoxyribose- and thymine-based.
• Thermal decomposition of thymidine is observed to start around 138 °C.
• Degradation process is explained by the rupture of glycosidic bond.
• Appearance energies of thymidine and its fragments did not depend on temperature.

Fragmentation of gas phase thymidine at different temperatures was studied with vacuum ultraviolet radiation and time-of-flight spectroscopy. Partial ion yield measurements were carried out in order to study the appearance energies of thymidine and its main fragments. The appearance energies of thymidine and its deoxyribose- and thymine-based fragments were determined to be 8.39, 8.77 and 8.81 eV, independently of temperature. The thermal decomposition of the sample was observed to start around 138–139 °C and it was explained by the breakage of the glycosidic bond, accompanied by hydrogen transfer from the deoxyribose ring to the thymine base.

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