Spectrometer interview Questions

Spectrometer interview Questions contains following questions

1. What is spectrometer? What are components of spectrometer?
2. What is a spectrum, spectral lines, Fluorescence spectroscopy?
3. What is pseudopotential, core electrons, solid structure, and method?

1. What is spectrometer ? what are components of spectrometer ?

Spectrometers are used to observe the spectrum of the energy transition in a sample of interest. Experimental spectrometer contains the following components,

Sample:

The sample to be detected for spectrum is kept in the sample holder.

This sample holder should be transparent to the radiation that we are going to use for the test.

For example if we are using UV below 2000 angstroms air becomes opaque in that case we must use a vacuum chamber for the observation.

Radiation source:

Radiation source is chosen according to sample we are testing.

For absorption spectra in the visible and ultraviolet regions older sources were the standard types of continuous light sources: tungsten filament lamps, electric discharges and arcs, spectrum tunable lasers are also available. In emission spectroscopy, the sample is the radiation source.

In this the sample is heated, by electric discharge, by radiation or by chemical reaction.

Optical system:

The optical system is usually used to select or disperse the radiation of different wavelengths and collect it at detectors.

Usually, prisms and lenses can be used as optical system. Other systems like, diffraction gratings, dispersing elements can also used.

Detector:

This is to detect the radiation coming from the sample for intensity measurement.

This is designed in such a way that it will record and display the relation between wavelength and intensity.

Normally a photographic emulsion is used as a detector. In visible and ultraviolet regions, photosensitive semiconductors are used.

In infrared region thermocouples and bolometers are used. In microwave region, crystal diodes are used.

2. What is a spectrum, spectral lines, Fluorescence spectroscopy?

Spectrum:

spectrum is representation of the amount of absorption as a function of wavelength or frequency.

Fluorescence spectroscopy is a process of exciting emission spectra, usually by excitation with radiation.

In this process one may measure the distribution of wavelengths of emitted radiation, as in any other kind of emission spectroscopy.

Emission spectroscopy, Absorption spectroscopy, Energy level trasitions

Emission spectroscopy

In emission spectroscopy, sample is subjected to thermal, electrical, or other excitation, and the excited atoms or molecules emit energy as they drop to lower energy levels. The emitted radiation is collected at the detector and its intensity is measure as a function of wavelength.

Absorption spectroscopy

In Absorption spectroscopy, a sample of material to be studied is subjected to radiation in desired part of the spectrum, and the molecules absorb energy, under going transitions to higher energy levels. This results in a series of spectral lines . This radiation is collected at the detector and its intensity is measured.

3. What is pseudopotential, core electrons, solid structure, method?

Pseudopotential:

The property of the solids depend upon the electrons in valence-conduction bands and these electrons which move in the solid are found outside the atomic core. Thus we should concerned about the description of the wave function outside the atomic core. Hence, the pseudo-potential is one which gives rise to essentially the same wave function outside the atomic core as the original atomic potential.

Pseudo-potential concept is to replace the atomic potentials by a weak potential which gives rise to the same scattering amplitude for the conduction electrons

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Spectrometer interview Questions