Acetone - Water Clusters Multiphoton Ionization Mass Spectrometry

The study of cluster is the cross field of physics, chemistry and biology etc. Molecular clusters are usually developed through Vander Waals weak interaction and hydrogen-bonded action. The clusters which are formed through hydrogen-bonded are specially important in many chemical and biological processes. In this paper, we mainly introduce the different hydrogen bond clusters formed between acetone and water by changing the wavelength of laser.In this work, we first got the acetone-water clusters by supersonic jet system. Then the multiphoton ionization signals of acetone-water cluster were detected by using the nanosecond laser which have the 355nm and 532nm wavelength respectively and the time-of-fight mass spectrometer (TOF-MS)systems. In order to investigate the configurations, energies and electric charge distributings of the hydrogen-bonded clusters, the ab-initio calculation was used on Gaussian 98 program. The mainly innovation and conclusion of this paper are as followings:1. It is the first time that the acetone-water cluster signals were detected at 355nm and 532nm laser respectively by using supersonic jet. The experiments showed that all acetone-water clusters were protonated at 355nm. We can conclude three main produces as (CH₃COCH₃)_n(H₂O)_n-2H⁺ , (CH₃COCH₃)_n(H₂O)_n-1H⁺ and (CH₃COCH₃)_n(H₂O)nH⁺. The same experimentation was done at 532nm laser. But the produce was only CH₃COCH₃-H₂O⁺ cluster at this laser. From above, we can conclude that the protonated cluster ions are mainly coming from the dissociation of larger acetone-water cluster ions and the non-protonated cluster ions are the perpendicular ionizing produces of the neutral clusters by absorbing photons.2. In the same experimental condition the multiphoton ionization mass spectrum of formaldehyde, acetone and butanone were all detected at 355nm. The results showed that only acetone can formed protonated cluster ions.3. The stable structures of the ionic clusters were given in the work by using ab-initio method and B3LPY method. Besides, the energy and electric charge distributing of the clusters were even given. All work was done on Gaussian 98 Program.4. The multiphoton ionization-dissociation produces of the methylamine dimmer were detected by using TOF-MS technology combined with tunable dye laser at 233-243nm laser.