Nitrobenzene And 2 - Nitrotoluene Multiphoton Dissociation Mass Spectrometry,

Molecular reaction dynamics is an interdisciplinary science in the field of physics and contemporary chemistry.It makes use of present advanced analytical methods about physical chemistry to study on dynamic structure,reaction process and mechanism of molecular primitives for different states and different elements in atomic and molecular level.It has been become a new subject in recent years and the forefront of the field of chemical kinetics.Since the thirties of this century,the development of spectroscopy and theoretical physics in the molecular structure promotes the chemical kinetics from the macroscopical to the microcosmic. And the rapid development of laser technology has greatly promoted the development of micro-reaction kinetics.Laser has some good features,such as homochromatism,polarization, coherence,ultrashort pulse,high-brightness and so on.It has become a powerful tool on selecting the reactant states and measuring the primitive products.Laser mass spectrometry analysis combes with resonance-enhanced multiphoton ionization (REMPI) and time of flight mass spectrometry(TOF-MS).It has become an important experimental method.Multiphoton ionization dissociation(MPID) is the process that when the molecules obtain energy by multi-photon excitation,they would divide into small fragments by breaking chemical bonds of molecules or ions after ionization.The ions that have same kinetic energy but different ratio of mass vs electric charge,will need different time when transit the same distance in the stable electric field.Time of flight mass spectrometry(TOFMS) is one of mass spectrometry analytical mothods that measure the elements and structure of matter using the above rule.The advantage of laser mass spectrometry theoretically is that very fast response speed,high sensitivity and no limit of mass.The article has two parts mainly.PartⅠis that the experiment is done to obtain the time of flight mass spectrometry of nitrobenzene about resonance-enhanced multiphoton ionization at laser 266 nm.The dynamic yielding of heavy fragment ions are discussed based on the measurement of mass spectrum.The main dissociation pathways are promoted.PartⅡis that the experiment is done to obtain the time of flight mass spectrometry of o-nitrotoluene about resonance-enhanced multiphoton ionization at laser 266 nm.Excitation Energy and oscillator strengths are computed by Gauss 03 programme with the basic of B3LYP/6-311++G(d,p).The dissociation rate and lifetime are also computed based on RRKM theory.The dynamic yielding of heavy fragment ions are discussed and the main dissociation pathways are promoted.Contents of this article are as follows:1.Development and application about multiphoton ionization and mass spectrometry.2.Experiment equipment and method.3.Studies about multiphoton dissociation mass spectrometry of nitrobenzene.4.Studies about multiphoton dissociation mass spectrometry of o-nitrotoluene.