| This dissertation can be divided into two parts:investigating the photodissociation of molecules under femtosecond laser field by ion velocity imaging technique and the structure and property of some compounds by low temperature negative ion photoelectron spectroscopy. The primary contents in this dissertation are summarized as below:Chapter 1 mainly introduced the ionization-dissociation process in intense femtosecond laser field, and the principle as well as the property of the low temperature photoelectron spectroscopy. The experimental setup of the direct current slice ion velocity imaging and low temperature photoelectron spectroscopy are described in Chapter 2.In Chapter 3, we experimentally demonstrate the photodissociation process of Br2 molecules in the intense femtosecond laser field by a dc-sliced ion velocity map imaging technique. We show that four fragment ions Brn+ (n= 1-4) are observed, and their kinetic energy increases while their angular distribution decreases with the increase of the charge number. We prove that the low (or high) charged fragment ions result from the photodissociation of the low (or high) charged parent ions. We explain the changes of the kinetic energy and angular distribution in these fragment ions by considering the potential energy curves of these parent ions that involve both the interaction of the Coulomb repulsive energy and chemical bonding energy. We also explain the experimental observation that the measured kinetic energy release in the experiment is much smaller than the theoretical calculation by enhanced ionization at a critical distance.Chapter 4 reports a comparison of the character of [MnO4·H2O]-, [MnO4·K·Cl]-and [MnO4·H·Cl]- anions using low temperature negative ion photoelectron spectroscopy. These study show that the H2O exists as a solvation molecule, the KCl is attracted by pure electronic interaction, both of which do not affect the MnO4 anion too much, but when adding HCl to the system, not only the ADE and VDE has been changed, but also the interaction and the molecular orbital has great difference in the system. By adding more H+ to the MnO4 ions, the oxygen can be taken away in the form of water molecule and leave the MnOn+(n=1-3) electron deficient. The Cl- ions thus can be oxidized.Chapter 5 presents a low temperature negative ion photoelectron spectroscopic study on tetraoxacalix[2]arene[2]triazine 1 as a charge-neutral molecular host to probe its interactions with a series of anions with distinctly different shapes and charge states. The binding energies of the resultant gaseous 1:1 complexes (1·Cl-, 1·Br-,1·I-, 1·SCN-,1·NO3-,1·IO3- and 1·SO42-) were directly measured experimentally, exhibiting substantial non-covalent interactions with pronounced anion specific effects. The binding strengths of Cl-, NO3-,IO3-with 1 are found to be strongest among all singly charged anions but only about 40% of that between 1 and SO42-. Electron density surface and charge distribution analyses further support anion-π binding formation. By dividing 1 into two subsystem, we find that the H-bond interaction contributes more than anion-π interaction in electron binding.In Chapter 6, we report a new class of superhalogen species, a series of tetracoordinated organoboron anions [BL4]-(L= phenyl (1),4-fluorophenyl (2), 1-imidazolyl (3), L4= H(pyrazolyl)3 (4)) with bulky organic ligands covalently bound to the central B atom using negative ion photoelectron spectroscopy. All of these anions possess electron binding energy higher than that of Cl-of 3.61 eV. First-principles calculations confirmed high EBEs and predicted that these anions are thermodynamically stable against fragmentation. The unraveled superhalogen nature of these species provides a molecular basis to explain the wide-ranging applications of tetraphenylborate (TPB) (1) and trispyrazolylborate (Tp) (4) in many areas spanning from industrial waste treatment to soft material synthesis and organometallic chemistry. |
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