Flame spectrometer is an instrument used for the analysis of emission and absorption characteristics of different materials. Holmarc's Flame spectrometer (Model No: HO-ED-S-03A) is able to analyze the spectrum of samples repeatedly with high speed. As we know, German Physicists Robert Bunsen and Gustav Kirchhoff discovered the spectral emission activity in the 18th century, which is modified here.
We use sodium metal for the experiment, which is placed in crucible and heated with Bunsen burner. Light from sodium flame is coupled to an optical fiber and taken to input port of the spectrometer. The output of the spectrometer produces standard D1 & D2 lines. In turn, in absorption spectroscopy, partially continuous spectrum of halogen lamp passes through the sodium flame. The cooler atoms in the centre of the flame absorbs certain region of halogen spectrum which produce D1 and D2 lines as absorbed dip lines. However, absorption or emission spectra will reveal the spectral characteristics of the material.
Holmarc's flame spectrometer is calibrated using mercury source which uses Hartmann’s constants as calibration method. It can be upgraded for research purpose and can be used to analyze absolute transmittance or reflectance spectroscopy by small modifications. CCD linear array detector is used in prism spectrometer. It will support UV-VIS-Near IR regions.
A safety cage design is used in flame spectrometer as a security systemfor controlling sodium metal hyper reactions. Cage is made of float glass for safety and visibility. Gas tube attached to Bunsen burner is protected using metal cover. Metallic crucible in fine size allows safe melting of sodium. Safety goggles are provided with the equipment.
We use low pressure Hg source & cubic or 3rd order polynomial equation for calculating the wavelength of spectral lines in concave grating spectrometer,
The cubic polynomial equation is
a x3 + b x2 + c x + d
Where a, b, c, d are constants of equation which is calculated by regression /curve-fit method using MS Excel.
Flame produced by Na metal shows dip lines in a tungsten halogen continuous source. The cooler atoms in flames centre shows normal absorption lines d1 & d2 which is around 589 & 589.6nm. The 6A resolution obtained using the polynomial calculation described above.
The contradictory emission spectrum shows the same d1 & d2 lines which reveals the characteristics of the element.