Communication: Vacuum ultraviolet laser photodissociation studies of small molecules by the vacuum ultraviolet laser photoionization time-sliced velocity-mapped ion imaging method

Pan, Yang; Gao, Hong; Yang, Lei; Zhou, Jingang; Ng, C. Y.; Jackson, William M.

doi:10.1063/1.3626867

Single-crystal calcium fluorite (CaF2) is widely used for transmissive optics in ultraviolet and vacuum ultraviolet (UV and VUV) wavelength applications because of its exceptional transmission performance. Generally, products using CaF2 are manufactured through finishing processes such as chemo-mechanical polishing (CMP), magnetorheological finishing (MRF) or ion-beam figuring (IBF) after performing precision cutting and grinding processes for profiling. However, CaF2 is known as a brittle material with high anisotropy, and subsurface damage is induced by each cutting process. But, the effects of surface integrity on the optical and functional performance of precision machined CaF2 has not been reported yet. In this research, a newly developed multiaxial adjustment system that can precisely align specimens is used in single-axis orthogonal cutting experiments with zero degree and negative rake angle diamond radius tools to prevent pre-machining and thus pre-damaging of single-crystal CaF2 specimens. Cutting forces evaluation via piezoelectric dynamometer acquisition as well as surface analysis by atomic force microscopy and white light microscopy has been performed. Finally, smooth surfaces due to ductile material removal mechanisms could be determined on all machined specimen surfaces.

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