Ozonolysis is an important sink of alkenes in the troposphere, which generates energized carbonyl oxide species (R1R2C=O+O-) known as Criegee intermediates. Their subsequent unimolecular decay is a significant source of an atmospherically important oxidant, hydroxyl radicals, and their bimolecular reactions can lead to secondary organic aerosol formation. In the laboratory, the Criegee intermediates are generated by an alternative synthetic route in a quartz capillary reactor prior to supersonic jet cooling, and are characterized on their strong π←π transitions by electronic spectroscopy and subsequent dissociation dynamics. Criegee intermediates exhibit broad ultraviolet-visible spectra with strong absorption cross sections associated with the carbonyl oxide group. Electronic excitation of Criegee intermediates accesses repulsive regions of ππ excited state(s), resulting in rapid dissociation to O-atom and carbonyl products. Velocity map imaging (VMI) is then used to determine the angular and velocity distributions of the O-atom products. VMI experiments of the formaldehyde oxide Criegee intermediate [CH2OO] reveal a bimodal total kinetic energy release (TKER) distribution for the O (1D) + H2CO (S0) products. The two TKER components arise from distinctly different pathways on multiple potential energy surfaces that lead to dissociation. The photodissociation dynamics of the dimethyl-substituted acetone oxide Criegee intermediate [(CH3)2COO] result in a much narrower TKER distribution of O (1D) + (CH3)2CO (S0) products and lack energetically accessible O (3P) + (CH3)2CO (T1) products. The electronic absorption spectra for the first π←π transition of methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide), derived from isoprene ozonolysis in the troposphere, along with the isomeric 2-butenal oxide Criegee intermediate demonstrate a significant spectral shift of ca. 50 nm to longer wavelength compared to alkyl-substituted Criegee intermediates due to extended conjugation across the vinyl and carbonyl oxide groups. Electronic excitation of MVK-oxide on its second π←π transition, associated with the vinyl group, exhibits weaker absorption cross section and a bimodal TKER distribution, the latter likely originating from different dissociation pathways. Finally, a reduced impulsive model is introduced to simulate the TKER distributions of the Criegee intermediates, providing insights on the energy partitioning during the dissociation process.