Development and Application of a Ultra-wide-band Photodissociation Spectroscopy System Based on a Fourier Transform Ion Cyclotron Resonance Mass Spectrometer

The method of photodissociation spectroscopy based on mass spectrometry was rapidly developed and widely applied in gas phase ionic chemistry and analytical chemistry due to its high sensitivity and feasibility in recent years. In this research, an optical system with ultra-wide-band tunable laser output was constructed and combined with a 7.0 T Fourier transfer ion cyclotron resonance mass spectrometer (FT ICR MS). The system could be used to acquire “Action” spectra of isolated ions. Compared with the traditional absorption spectroscopy, it had the advantage of high sensitivity, which could completely eliminate influence of impurities and solvents. After its generation, the target ion could be selected in FT ICR cell, and irradiated by laser with different wavelengths. The energy obtained after absorbing photons at appropriate wavelengths could cause the ions to dissociate and to form fragment ions to be detected. By gradually changing the wavelength of laser and analyzing the mass spectra under different wavelengths, the photodissociation spectra of target ions could be obtained through data analysis. The system applied here could be used to obtain ultra-wide-band photodissociation spectra of different ions in the gas phase. The full spectral tunable range of the system was 192-3 700 nm, which was, as far as we knew, the widest available tunable spectral range fulfilled on a single mass spectrometer. The ultra wide wavelength coverage was realized by two wavelength tunable OPO lasers. The optical path was set in vacuum, which improved the transmission efficiency of lasers in ultraviolet and infrared regions. The system combined the advantages of electrospray ionization (ESI), high mass resolution and superior ion handling capability of FT ICR MS. The UV-visible and mid-infrared photodissociation spectra of the target ion could be obtained, which were complementary, corresponding to their electronic and vibrational energy levels of molecules, respectively. Since the full spectrum for some target ion was generated under the same ion source, it avoided some unexpected spectral differences caused by ionization conditions and other instrument-relative factors. In this paper, rhodamine 110 and tryptamine were taken as examples. Photodissociation spectra of corresponding ions in different wavelength range were obtained, which preliminarily proved the feasibility of the method.