Introduction to Spectroscopy.

Transcription

1 Introduction to Spectroscopy. ARCHIMEJ TECHNOLOGY The SPECTROSCOPY 2.0 Company To understand what the core of our project is about, you need to grasp some basic notions of optical spectroscopy. This lesson will give you some insights on our technology and its applications.

2 What s Spectroscopy? SPECTRO - SCOPY spectrum study spectrum - science Spectroscopy: The science of the spectrum First things first. Our technology is called Spectroscopy 2.0 but I think that spectroscopy is rather difficult to understand for those who haven t undertaken physics studies. By definition, it s the science of the spectrum. How can we define the spectrum then?

3 Spectrum? Counts Characteristic A spectrum is in fact an histogram that consists in the counting of objects according to a specific characteristic.

4 Music Sound Waves classification Amplitude Frequency 440Hz For example, the most common spectrum is the sound s and more specifically, the one that allows to characterize music. The characteristic here is the frequency of the sound wave which also defines the pitch of the note and the amplitude of each pitch is counted. What we get at the end is a histogram as defined previously.

5 Optical spectroscopy Counts: Intensity Joule per Second Watt per Steradian Photon per Electron Light classification Wavelength λ: nm, um, cm -1 khz, Thz ev Our work is focused on the Optical Spectroscopy which is the classification of the light according to its wavelength. The wavelength, that is inversely proportional to frequency is also what defines the color of the light. It works the same way as the previous example, we measure and count a predefined amplitude of the light such as its intensity according to the wavelength.

6 Light spectrum What is commonly called light spectrum is actually a part of the electromagnetic spectrum and visible light constitutes only a fraction of the whole spectrum. Inside this spectrum we can find anything from radio waves to gamma rays that are emitted by radioactive elements.

7 What s (optical) spectroscopy? Definition: The study of the light spectrum.

8 Optical spectroscopy Spectroscopy is based on the 3 interactions of Light with Matter Emission : The light created depends of the source properties. Depending on the properties of the source, the light created will have unique properties that are measurable. Absorption : The light changes depends of the sample properties The intensity of light will be modified if this light goes through a medium Scattering : The light created depends of the sample and source properties If the light encounters an obstacle, its direction will change following its wavelength.

9 What s Light? Before 1500 One of the 5 elements: 土木金火水 One of the 4 elements: Fire Air Water Earth ~1600 A particle that travels in straight lines. ~1800 A wave oscillating in the aether An electromagnetic radiation traveling through void 1905-today: A flow of quantum energy wave-particles (photons)

10 What s Light? A flow of photons Albert Einstein : Every fool thinks he knows what the photon is. But he is mistaken.

11 What s Matter? The short answer: Matter is a pack of atoms

12 What s Matter? From minerals to life forms, everything is a result of complex interactions of atoms

13 How Light is created? Incandescence: When something is very hot (molecular agitation), it makes light

14 How Light is created? Electric discharge: When the atoms of a gas get excited, they make light

15 How Light is created? But also: Electroluminescence : The Light-Emitting Diode or LED is the source we have chosen for our technology because of its numerous qualities in terms of spectral and electrical properties. Stimulated emission : A Light Amplification by Stimulated Emission of Radiation or LASER is device that emits light through a process of optical amplification. Others : There are also other means of emitting light such as fluorescence or bioluminescence.

16 Absorption spectroscopy Our project concerns absorption spectroscopy which means that we want to see how a sample will modify a well-known light intensities so we can know what constitutes the samples.

17 Absorption spectroscopy Spectrometer : Machine that measures the light spectrum. There is a light source we perfectly know the spectrum, the light it emits go through the sample we want to characterize and it is then separated (for instance by a prism or a grating) so we can know how much each wavelength was absorbed when the light intensity is measured by a light detector (CCD of Photodiode, for instance)

18 Work principle of a spectrometer The state of the art of the light source is to cover a wide range of wavelengths by using black bodies, mercury lamps or x-ray tubes, in order to measure a broad region of the absorption spectrum. Then, the spectrometer spatially separates the wavelength of the light beam using gratings or filters, in order to independently measure the intensity of each wavelength of interest with broadband detectors or single detectors matrix. Spectroscopy 2.0 arises from the total re- imagination of the spectrometer composing blocks, on one side, and from the LEDs revolution, which allows to dispose of quasi- monochromatic chips able to emit in any wavelength (UV, Visible, NIR) on the other. Focusing on dynamic, spectral and temporal control of the light source, Spectroscopy 2.0 makes the separation of light spectrum to become unnecessary.

19 ARCHIMEJ TECHNOLOGY Thank you for your attention This was a very basic introduction to Spectroscopy, we hope that now, you have a better understanding of what we are working on. If you want more information, and we encourage curiosity, do not hesitate to directly ask us!