Spectroscopy Flashcards
What is spectroscopy?
The study of the interaction of radiation with matter
Describe atomic absorption spectroscopy?
Electrons can gain energy by the absorption of energy in a photon which causes electronic transition
What happens in an electronic transition?
The electrons are promoted to a higher energy level
What does the energy of the absorbed photon correspond to?
The energy difference between the upper and lower energy levels
What will the absorbed photon have?
A specific frequency and wavelength I.e. A specific energy
What happens to the sample during atomic absorption spectroscopy?
The sample is vaporised and placed in the path of em radiation (white light/ all wavelengths).
Incident light > sample > transmitted light
(All wavelength). (Wavelengths missing)
Absorption by the sample will remove some of the photons from the em radiation (the energy is used to promote electrons to higher energy levels)
What does an absorption spectrum measure?
How a samples transition of light varies with wavelength
What does an atomic absorption spectrum appear as?
Dark lines on a continuous spectrum
What do the dark lines correspond to?
Wavelengths of light that have been absorbed by the sample
What are electronically excited states of ATOMS generated by?
High voltage electric discharges through the sample, or by high temperatures
Describe atomic emission spectroscopy ?
The electrons lose their excitation energy by returning to the ground stage. This is accompanied by the emission of a photon
What does the emitted photon have?
A specific frequency
If each electronic transmission has a specific energy value, what does this mean for the emission of electromagnetic radiation?
It has a specific frequency and wavelength
What does a typical emission spectra consist of ?
A series of coloured line on a dark background
What does each line correspond to ?
A specific electronic transition and therefore frequency
What does the emission spectrum of hydrogen consist of?
A series of lines in different regions of the em spectrum
What do the lines in the emission spectrum of hydrogen arise from?
Many transitons from upper energy levels to lower energy levels
What is absorption and emission spectroscopy used to do?
Identify and quantify the elements present in a sample
What does each element produce?
A characteristic absorption and emission spectrum that an be used to identify the element
What does the intensity of the lone provide?
A measure of the quantity of an element which may be present in a sample
What happens to the lines in an emission spectrum at high energy end of the spectrum ?
The lines converge
Why does the convergence limit arise?
Because energy levels in an atom get closer together with increasing distance from the nucleus
What is the convergence limit in an emission spectrum?
The point where the electron falls from the highest energy level to the ground state
What is the energy produced by this transition approximately equal to?
The energy required to remove the electron from the atom I.e. The ionisation energy
