TRMC cell
The left image shows the front or window part of the cell: Via the grid, sealed with a quartz window light enters the cell. The full length of the cavity is designed in such a way that it can contain one full oscillation of the microwaves. The sample consisting of the photoactive material on a quartz substrate fits exactly in the lower part, which is located at a quarter from the iris to maximize the signal strength. Typically, samples are mounted in the cell within the glovebox to ensure exclusion of oxygen and moisture.
The right images shows the difference of an "iris cell" with a so called "open cel". The iris cell is at least 10 times more sensitive at the cost of temporal resolution: the rise time is lowered from about a nanosecond to 18 ns for this iris size.