科研之友
微信
新浪微博
Facebook
分享链接
摘要
The desorption dynamics of tetracene ion ([tetracene](+)) from tetracene-doped anthracene (TDA) crystals in which efficient energy transfer from anthracene to tetracene occurs was investigated by means of femtosecond time-resolved mass spectrometry. Using a 400 nm pump pulse, anthracene molecules in TDA crystals are initially excited to the SI state. After a certain delay (%26lt;10 ps) of pumping, the excitation energy in the SI anthracene is transferred to a tetracene molecule to produce the SI state. Tetracene in the S-1 state is then ionized by a time-delayed probe pulse (266 nm) and desorbed tetracene ions from the crystals are monitored with a time-of-flight mass spectrometer. On the time-resolved mass spectra, the peak intensity of the tetracene ions shows a gradual increase with increasing delay time. The rise time constant of tetracene ion, which is considered to the desorption time from the crystals, was determined to be 80.8 and 94.7 Ps for TDA crystals with anthracene/tetracene concentration ratios of 1:0.02 1:0.01, respectively. The desorption time of tetracene ion became short with increasing excitation power. The So anthracene at the highly vibrationally excited state is produced by internal conversion or exciton-exciton annihilation of electronically excited anthracene molecules, and the excess vibrational energy stored in anthracene is considered to be the origin of the vibrational excitation of dissociative modes, which leads to the desorption of tetracene ions. We also consider that the present process, which includes electronic relaxation and the production of excess vibrational energy in the ground state of matrix molecules, is the mechanism for the desorption of analyte in conventional matrix-assisted laser desorption ionization (MALDI).
- 出版日期2012-2-2
