This is a quarter-meter monochromator with three interchangeable gratings. The Jarrell-Ash model number is 82-499, serial number 998527. The gratings are selected via a large knob on top of the unit. Wavelength is selected via a small crank that drives the grating table via a urethane toothed belt, with a mechanical digital readout of the table position on the top of the unit.

There is a full complement of gratings installed as follows:

Pos. 1 – 300 g/mm, blaze 300nm (part number 985-30-39-18)
Pos. 2 – 600 g/mm, blaze 500nm (part number 985-30-29-22)
Pos. 3 – 150 g/mm, blaze 450nm (part number 985-30-49-21)

The entrance port has a single fixed-slit holder installed (no slit supplied), and the exit port has a circular flange for mounting a detector.

All of the optics in the system are in spectacular condition – the collimation mirrors and the diverter mirrors all appear to be free of any blemish and without haze. I was unable to see any defects in any of the gratings.

One issue does require attention – the toothed drive belt for the wavelength selection has started to deteriorate, and one portion of the belt slips. It is in urgent need of replacement If the counter is supposed to be synchronized to a particular grating, then it will need to be reset when the new belt is installed. Otherwise, this is in mechanically near-flawless condition. No evidence of rust, and interior is near-spotless.

Location H2 R5

Photo set 809