Perkin Elmer Lambda 950

PerkinElmer

Device name: PerkinElmer - UV/VIS spektrometer

Model: LAMBDA 950

Device responsibles: Stephan Dottermusch, Raphael Schmager

Room: R203

Wavelength range: 175 - 3300 nm

UV/Vis resolution: ≤ 0.05 nm

NIR resolution: ≤ 0.20 nm

Dimensions (W x D x H): 1020 mm x 630 mm x 300 mm

Short description

The LAMBDA 950 is a spectrometer for measuring the reflection, absorption und transmission of diffrenct samples in a wavelength range from 170nm bis 3300nm. A build-in InGaAs integrating sphere enables measurement of diffuse scattered light.

Important rules

a. When turning off the device wait for at least 10 minutes before turning it on again. Otherwise you will damage the lamps.

b. Always turn off the lamps if the device is not used for a while. If not used for a longer period, turn the device off completely! If someone has an appointment shortly after you – please coordinate.

Getting started

a. Turn on the device and turn on the computer; don’t start the software immediately.

b. Wait a few minutes before starting the software. Otherwise you might encounter problems during your measurement as the device could not properly set itself up.

c. A useful tool for setup is “manual control”. Here you can apply different settings for observing the changes in beam size, detector signal, make quick measurement at a single wavelength, etc.

Go to “Instruments”, click on “LAM950”, and select “Manual Control”.

d. Measurements are usually performed with “Scan”.

e. Always check the complete beam path. Are there obstacles? A lens? An iris? Is the reflection standard at the end installed?

Scanning

I D2 lamped used for UV measurement from ~190 nm to ~320 nm. Wavelength as low as 175 nm are possible if purging the system with nitrogen. The tungsten lamp is used for measurements from 320 nm to 3300 nm. Default for the lamp change is 319.2 nm. Values between 300 nm and 350 nm can be used if plausible for your measurement. Higher or lower values can damage the system.

II Two different monochromators are installed - intended for use with the different detectors. The switch in monochromator and detector should occur at the same wavelength (default: 860.8 nm). Values outside the range 700 nm to 900 nm can damage the system. Ideally the switch should occur where the sensitivity of the two detectors is nearly the same.

III The slit width defines the spectral width of the used spectrum. Due to the difference in monochromators similar beam shapes are achieved if the InGaAs slit width is 4 times the PMT slit width (PMT 2 nm -> InGaAs 8 nm). Servo control is available for InGaAs detection. The slit width will then vary to keep the detection rate constant. The lower the detector sensitivity (or lamp output) the larger the slit width. Control of the slit width is possible via the Gain.

IV The gain is an electrical gain at the detector. Gain should be high enough for a signal to be detected and low enough not to cause saturation of the detector. Use “manual control” and the energy mode E1 and E2 to monitor the effect of different gains at different wavelengths. Saturation occurs for E1 or E2 > 100. The gain should be chosen such that the highest achieved value in the measurement range is ≈80 for E1 and E2

V The response is the integration time at every wavelength. The higher the response the longer the measurement will take, but a higher signal to noise ratio is achieved. One chopper cycle is 0.04 s.

VI The common beam mask (CBM) reduces the beam height, but also drastically reduces the beam intensity. For significant effects values below 50% are necessary. The change in beam size is most effective in the sample compartment and at the reflection port of the integration sphere. Almost no effect can be observed at other positions.

VII Of the three components shown here only the attenuators are installed in our system. The beam is polarized (!) and the polarization cannot be controlled in the system directly. Here is a graph of the beam polarization. 1: totally “TE” polarized; 0: unpolarized light; -1: totally “TM” polarized.

Operation Modes

%T Most straightforward mode of operation. The system first takes a reference spectrum (I0) and then your measurement spectrum (I). The output is I/I0 in percent.

%R Output identical to %T. But the use of “corrections” is possible. Corrections are never necessary if your sample is positioned in front of the integrating sphere (measuring transmission). They might be important if your sample is positioned inside (measuring absorption) or at the back port of the sphere (measuring reflection).

Especially when measuring reflection slight offsets can occur. Examples:

1. The cover lid on the reflection port is black, but not a perfect absorber. Light will partially be reflected and travel back through your sample into the integrating sphere. This is important when measuring the reflection of highly transmitting samples. It will lead to a constant offset of ≈1%. Taking the 0% “blocked beam” baseline (not using the internal attenuators) without the reflection standard is necessary for high precision measurements.

2. If your sample is a great reflector it might be an even better reflector than the white spectralon (R ≈99% in the visible). In this case I > I0 you will therefore measure R > 100 %. You will need to active “Reflectance corrected for reference (%RC)” and select an appropriate “Light Spectral Reference”.

A Same data as in %T is taken. But the output is A = - log10(I/I0).

E1 / E2 Energy output of the detector (Sample beam (E1) / reference beam (E2)). The values have no physical meaning. The data is a combination of the light intensity at a given wavelength, the detector sensitivity at that wavelength and the detector gain. No reference is applied to the data. Looking at these values can make sense for determining errors. Lower values mean little signal. A red exclamation mark means the detector is saturated.

More useful information

High absorbing samples

The system is equipped with a chopper for lock-in amplification. Additionally this chopper makes a continuous switching between the reference beam and the sample beam possible (Cycle time 0.04s), so they are never “on” at the same time. Problems occur if one of the beams is much stronger than the other. This is the case if a highly absorbing sample (A > 4) is placed in the sample beam. To prevent unwanted effects the refrence beam needs to be attenuated using the internal attanuators. A 0% blocked beam reference (using the internal attenuators) should also be taken for high precision measurements (corrections).

Small area and inhomogenious samples

For small areas and inhomogenious samples precise measurements can only be taken if the beam shape is kept constant. This is especially important at the detector switch. Intensity should not be too low and the “multible of 4 rule” (see section C.III) should be maintained. Blends and lenes, available in a dawer underneath the PerkinElmer, can be used for reducing the beam size. Blends can be most easiliy be placed in the sample compartment. Lenses are only effecful is placed directly infront of the integrating sphere.

Technische Doku

Technische Doku