To infinity and beyond…
…without ever leaving the lab. It may be hard to believe, but the technology used to explore deep space is the same that we use in our laboratories. Whether stargazing on the highest level – as in this image of the polar-ring galaxy 4650A located in the Centaurus constellation, taken by the ETH Zürich – or melting iron at the Brechmann-Guss foundry, we are all using technology predicated on the foundational work of Messrs. Kirchhoff, Foucault, and Bunsen from the 19th century. It was around the middle of that century that these gentlemen first managed to identify the characteristic radiation of sodium and other elements, and to find the connection between these emissions and the solar radiation spectrum as envisioned by Fraunhofer (atomic spectroscopy).
The technological process can be explained using a simple atomic model, in which the atom’s electrons orbit the nucleus along particular paths (within particular shells). Each of these shells can only hold a certain maximum number of electrons. The shell does not have to be completely full, but it cannot hold more electrons that the maximum number; any surplus electrons are “pushed” out to the next shell. The electrons in each of these shells possess a specific amount of energy that is characteristic for the given chemical element.
A sort of elemental fingerprint
The further a shell is from the nucleus, the higher the amount of energy is that it contains. As atoms strive towards a minimally energetic state, the electrons would prefer to drop down to a lower shell; however, since the shells have a maximum capacity, the electrons cannot do so unless there is a “free” spot for them to take.
This preference of electrons to “drop down” is made use of in emission spectroscopy: Energy is applied to the specimen (directly by applying a voltage, or with an electron beam), and electrons are “knocked out” of the inner shells. Outer electrons can now drop down and take these free spaces; however, since outer shells possess more energy, the electrons must get first rid of the surplus energy from the outer shell. This emitted energy takes the form of radiation, and is equal to the energy difference between the inner and outer shell. As the amount of energy in the shells is characteristic for each chemical element, these “packets” of emitted energy are also characteristic for each element – a sort of elemental fingerprint.
“packets” of emitted energy are characteristic for each element – this effect is used
In other words, by measuring the amount of radiation emitted by the material during the process (the size of the packets), it is possible to conclusively identify the chemical element. The spectrometer then separates and analyses the various sets of emissions, making it possible to identify which elements the material contains – as well as what percentage is composed of that element.
When a modern spectrometer analyses a cast iron specimen containing multiple chemical elements, it initially “sees” thousands of spectral lines from among an uncountable number produced by the various elements (one set from iron, one set from carbon, one from silicon, …). High-performance spectrometers can then separate and sort these thousands of lines into clusters.
The machine then analyses the energy and intensity of the spectral lines. The energy of the lines (the size of the packets) provides information about which chemical element(s) is (are) present. The intensity of the lines gives information about the concentration of the identified element in the sample – i.e., what percentage of the specimen consists of that element.
The spectrometer’s computer contains a database of calibration curves for possible chemical elements; the measured energies and intensities can then be compared to these calibration curves. When it finds a matching analytical curve, the computer can then identify the measured energy as belonging to the matching element. As a result, the computer can generate a complete analysis of the chemical composition of the specimen. This can be done for any specimen – whether cast iron with spheroidal graphite, with lamellar graphite, alloyed with SiMo, or with a high concentration of nickel (Ni-Resist).
The astronomers and astrophysicists at the ETH Zurich work in almost the same way – except that they are measuring light, and their considerations are on a galactic, rather than an atomic, scale…
Our goal may be slightly different, but it is true for us as for them, that Quality is our benchmark – and the bar is high!
Do you have any questions, don`t hesitate