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System Description . 29

The radiation passing alternately through the sample and reference beams is reflected by

mirrors M11, M12, M13, and M11′, M12′, M13′, respectively of the optics in the detector

assembly onto the appropriate detector. Mirror M14 is rotated to select the required detector.

A photomultiplier tube (PMT) detector is used in the UV/Vis range, while a lead sulfide (PbS)

detector is used in the NIR range. Detector change is automatic during monochromator

slewing.

NOTE: The PbS detector is not available in the Lambda 650 or 850 spectrometers.

At the cell plane, each radiation beam is approximately 12 mm high. The width of the

radiation beams is dependent on the slit width. At a slit width of 5 nm each radiation beam is

approximately 4.5 mm wide. To permit minimum sample volumes to be measured in micro

cells, the height of the radiation beam must be reduced in the active cell area.

A common beam mask (CBM) is mounted between the slit assembly (SA) and mirror M7. This

mask restricts the cross-section of both the sample beam and the reference beam in the

respective cell area. The radiation beam can be reduced from the maximum height of

11.7 mm to 0.0 mm in 50 steps.

During all scanning operations, the monochromators stop slewing while a filter, source, or

detector change is in progress.

NOTE: You can select the source or detector change wavelength within a defined

wavelength range. This facility is useful if a feature of special spectral interest is

located at one of the default change wavelengths.

The spectrometer scans from higher toward lower wavelengths.

There is an optional depolarizing filter (DP) accessory, which can be swung into the beam.

There are automatic internal attenuators for the Lambda 850 and 950 spectrometers that can

be swung individually into the sample beam (SBA) and the reference beam (RBA). The

attenuators have the values: 0%, 1%, 10% and 100%. The Lambda 650 and 750

spectrometers require manual attenuators to be placed over the ports in the sample

compartment wall as needed (L6020277 – 10% attenuator, L6020276 – 1% attenuator).

Lambda 1050 Spectrometer

The optical system of the Lambda 1050 is the same as for the Lambda 950 spectrometer,

with three exceptions.

First, there is a source doubling mirror M0 in the lamp compartment, designed to increase

the intensity of the light from the halogen lamp (HL) that is reflected by mirror M1 to mirror

M2.

PerkinElmer Lambda 650 User Manual

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