Water molecules play a very important role in many fields of planetary life, namely, in atmospheric, biological and chemical processes. Water clusters are multimers of water molecules held together by extensive hydrogen bond networks. They are formed by condensation of water vapor in the supersonic beam as it passes from the atmospheric to low pressure region of the source through an orifice. Recently, particular attention has been focused on studying water clusters, which exhibit many features of condensed phase, but have finite size. Whereas a huge number of papers have been published on photoionization of mixed clusters of water with alcohols or aromatic molecules few is known about photoionization of neat water clusters. The present work presents the results of the application of electron impact and laser ionization TOF-MS on water clusters up to 160 molecules in order to have information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. Laser pulses in nanosecond and picosecond range have been applied in order to test the possibility of extending the mass detection much over the previous published papers. A comparison between two configurations of TOF-MS detector, linear and reflectron, in water clusters spectral analysis is also reported in order to show the advantages of both for obtaining more complete information. A study of signal intensities of water clusters formed by using nanosecond and picosecond laser ionization vs laser pulse fluence concludes the work.
Photoionization study of water clusters
Apicella B;Wang X;
2013
Abstract
Water molecules play a very important role in many fields of planetary life, namely, in atmospheric, biological and chemical processes. Water clusters are multimers of water molecules held together by extensive hydrogen bond networks. They are formed by condensation of water vapor in the supersonic beam as it passes from the atmospheric to low pressure region of the source through an orifice. Recently, particular attention has been focused on studying water clusters, which exhibit many features of condensed phase, but have finite size. Whereas a huge number of papers have been published on photoionization of mixed clusters of water with alcohols or aromatic molecules few is known about photoionization of neat water clusters. The present work presents the results of the application of electron impact and laser ionization TOF-MS on water clusters up to 160 molecules in order to have information on the electronic states of clusters of different sizes up to dimensions that can approximate the bulk phase. Laser pulses in nanosecond and picosecond range have been applied in order to test the possibility of extending the mass detection much over the previous published papers. A comparison between two configurations of TOF-MS detector, linear and reflectron, in water clusters spectral analysis is also reported in order to show the advantages of both for obtaining more complete information. A study of signal intensities of water clusters formed by using nanosecond and picosecond laser ionization vs laser pulse fluence concludes the work.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
