Many thanks to student Alex Blackwood who filmed them using the Sony FS-700 camera, filming at 800 FPS.
An introduction to Spectroscopy: Flame tests
Spray bottles containing different chloride salts dissolved in a flammable liquid were used to demonstrate the presence and identification of certain elements.The colours emitted by copper = green, strontium = crimson red, barium= apple green, lithium = red and calcium = orange) are mainly due to thermal excitation (starting at about 500 ºC) of atoms and molecules in the gas phase. When the salts start to thermally decompose and in the presence of chlorine donors, new unstable short-lived species are formed (free radicals). These act as ''emitting species'' in which relaxation of the excited electrons (from a high to low energy level) causes emission of a photon with a specific wavelength in the visible part of the electromagnetic spectrum (400 -- 700nm).
You can also use inexpensive holographic diffraction grating glasses to see the individual spectrum emitted by each element and even take a photo using the camera on your mobile phone to observe the characteristic lines in each spectrum.
