Microscopic internal reflection infrared spectroscopy to examine the surface of a trace amount of material

摘要

A new set of mid-Infrared transparent elements with different geometries to enable examination of the sample surfaces by Internal Reflectance Micro Infrared Spectroscopy is disclosed. The Infrared beam from the IR microscope, either collimated or focused, enters the surface of the element and impinges on an inclined surface of contact between the sample and the element at an angle above the critical angle. This IR beam from the microscope operating in the reflectance mode is then internally reflected at the beveled surface cut at a selected angle, travels inside the IR element, reaches a circular reflector surface where it is reflected back to retrace its initial path. The beam once again comes in contact with the sample at the sample and the element interface and is reflected. The returning of the IR beam to retrace its original path without any significant loss of radiation is accomplished by the following methods: a) the circular end of the outer surface where the internally reflected beam strikes is mirrored from outside b) a retro mirror assembly is placed immediately outside the surface where the internally reflected beam strikes. The center of curvature of this mirror is configured to coincide with the center of curvature of the circular element at the point of contact between the sample and the element.