ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 51, Number 4
JKCSEZ 51(4)
August 20, 2007 

Electronic photofragmentation spectrum of protonated tyrosine-alanine dipeptide ions(YAH⁺) was obtained in the wavenumber region of 34500~36700 cm^-1 using a quadrupole ion trap time-of-flight mass spectrometer (QIT-TOFMS). YAH⁺ ions were produced by electrospray ionization, stored in the ion trap and then irradiated by ultraviolet laser pulses which induced photofragmentation of the ions. The electronic photofragmentation spectrum was obtained by monitoring the photodissociation yields of YAH⁺ ions as a function of the laser wavelength. The spectrum exhibited two broad peaks which were assigned as S₁ and S₂ by theoretical calculations using a time-dependent density functional method. The broad widths of the peaks in the spectrum were explained by the overlaps of the peaks originated from various conformers of YAH⁺ ions which were present in the gas phase at room temperature and also by the contributions of the hot bands.