Instrument's use : UV-Vis spectrophotometer

      The Nicolet Evolution 500 is a double beam spectrophotometer built around a robust aluminium base casting. The optical system is based around an Ebert Monochromator using a 1200 line/mm Holographic Grating. Slit sub-assemblies can be fitted to give variable bandwidth or one of 2 fixed bandwidths.

     Wavelength accuracy is achieved by software compensation. The calibration routine finds 9 predefined emission lines over the wavelength range using Mercury and Deuterium lamps, and uses these to characterise the instrument and so calculate the correct motor position for the requiered wavelength.

      There is provision for a Calibration Validation Unit (CVU); this fits in the sample beam just beyond the modulator. Calibration Validation can be performed eighter by measuring certain frequencies in the emission spectrum of the Mercury Lamp, or by using the Tungsten Halogen Lamp and a filter disk within the CVU driven by a motor under software control.

      The Evolution 500 uses two sources to cover the wavelength range specified. A Tungsten-halogen lamp provides the visible radiation and a Deuterium Arc lamp provides the UV radiation. In addition a Mercury lamp can be fitted for checking wavelength accuracy or recalibrating the instrument.

      The UV radiation source is a Deuterium Arc lamp with an inline connector, prealigned for your instrument. It has a low current heater which, once the lamp has been struck, remains on the maintain maximum low drift stability and a maximise lamp life. The Nicolet Evolution 500 spectrophotometer has a photomultiplier detector.

	Normal	High Absorbance
Auto (315-340 nm)	Constant signal at all wavelengths*	Constant signal at all wavelengths*
Tungsten	Constant signal from lamp change to 900nm, constant EHT from 190 nm to the lamp change (values taken from Normal table)	Constant signal from lamp change to 900nm, constant EHT from 190 nm to the lamp change (values taken from HAA table)
Deuterium	Constant signal from 190nm to lamp change, constant EHT above lamp change (values taken from Normal table)	Constant signal from 190nm to lamp change, constant EHT above lamp change (values taken from HAA table)

      The stepping monochromator design and advanced signal processing of the Evolution 500 instruments mean that wavelenght accuracy is independed of scan speed, therefore the main considerations in selecting scan speed will be the acceptable noise level on the spectrum.

     The standard scan speed options allows the setting of fixed scan speeds. The maximum rate at wich the spectrophotometer can scan is 1200 data points per minute. This equates to 2400 nm/min at 2nm data interval (or 120/min at 0.1nm data interval) with an integration time of 15 milliseconds. By slowing the scan speed and/or increasing the data interval the integration time can be increased and consequently noise decreased.

Absorbtion Spectra of Rhodamine B in etanol (conc.=9*10-6 mol/L)


Absorbtion Spectra of Rhodamine B in etanol at different concentrations