.1 - Naphthol Monochromatic Two-photon Ionization Mass Spectrometry Studies

Cluster is a relative steady microcosmic or sub-microcosmic congeries which is composed of several or even thousands of atoms or molecules through chemical or physical combining force.Molecules clusters are usually developed through Vander Waals weak interaction and hydrogen-bonded action.The study of the ionization using the laser of the clusters which are formed through hydrogen-bonded is the effective way to understand the composition of clusters, molecular reaction and transfer mechanism in the clusters.1-naphthol(1HN) is an important cresol.They can form hydrogen bond between OH and OH or OH and aromatic ring.In this article,we studied the ionization process of 1HN cluster in the UV laser using the super sonic pulsed molecule beam,time of flight mass spectrum.And combined the procedure of Gaussian 03 to research geometry structure and energy level structure of 1-naphthnol cluster.The including is following:(1) The effect of the laser wavelength to the cluster counts:the number of the trimer changed very slightly when the laser wavelength increasing while the numbers of the molecules and the dimers changed bigger.The peaks of the molecules appeared at the trough of the trimers and dimers.This mean the molecules were made by the dissociation of the trimers and the dimers.(2)The effect of the laser energy to the cluster counts:the dimphoton ionization mass spectrum of 1HN cluster on the 282.5nm,285nm,287.5nm and 290nm were studied under different laser intensity.A series of(1HN)_n⁺ cluster ions were observed in the time-of-flight mass spectrum,and the signal intensities of the higher clusters decreases with n.Ionization laser energies have relatively little effects to the cluster ions distribution,so soft ionization process may be dominant for the cluster ions production and the mass spectrum corresponds to the original neutral clusters population.There is no obviously signal of the fragments.The 1HN⁺ peak appeared to split.This may be the shift of the mass spectrum which caused by some internal overmuch energies being converted to the ions translational energies super that at higher ionization energy condition more quantity monomers were ionized with excited vibrational state which are produced by the internal energy transfer occurred by remained energies over its ionization needed.The shift is more obviously with the increase of the laser intensity and the photon energy.(3) The effect of the inlet pressures to the cluster counts:Inlet pressures were changed in the experiment.There were no signal of the fragment when the inlet pressures were small.Inlet pressures in the ionization area have obvious affection to the cluster ions formation where some new series ions produced between adjacent(1HN)_n⁺ cluster ions when the pressure increased. Such new produced cluster ions are associated with water clusters which are probably generated through intracluster reactions.(4) The theoretical calculation about 1HN:The different forms,electric charge distributing and structural parameters of the(1HN)₂ were given in the work by using DFT method combined the Gaussian 03 program.The causes of the(1HN)₂ were studied.Besides,the 1HN-C₆H₅OH and 1HN-H2O clusters were also calculated by the same basis set at the same level.The difference of hydrogen bonds in them were campared with the(1HN)₂′s...