What is a line shape function?

A line shape function is a (mathematical) function that models the shape of a spectral line (the line shape aka spectral line shape aka line profile). The specific shape of the line i.e., the intensity at each wavelength along the width of the line, is determined by characteristics of the source and the medium.

What is Lorentzian line shape?

The shape of lines in a nuclear magnetic resonance (NMR) spectrum is determined by the process of free induction decay. This decay is approximately exponential, so the line shape is Lorentzian.

What is the significance of line shape function in laser?

This implies that the atom can absorb or emit radiation over a range of frequencies Δ . This range is usually much less than . When a radiation is incident the strength of interaction of this energy state with radiation is a function of frequency. This function is called the line shape function.

Why are spectral lines broadened?

Spectral Line Shapes, Widths, and Shifts Observed spectral lines are always broadened, partly due to the finite resolution of the spectrometer and partly due to intrinsic physical causes. The principal physical causes of spectral line broadening are Doppler and pressure broadening.

What is line broadening?

line broadening, in spectroscopy, the spreading across a greater wavelength, or frequency range, of absorption lines (dark) or emission lines (bright) in the radiation received from some object.

What is the difference between Gaussian and Lorentzian?

The Gaussian curve is the classic ‘bell-shaped’ or ‘normal’ curve/distribution. The Lorentzian is somewhat narrower around its maximum and it extends out a little more than the Gaus- sian on its sides, i.e., the Lorentzian has ‘wings’.

What is collisional broadening?

Pressure broadening (also called collision broadening) is brought about by collisions between molecules or atoms, which can supply or remove small amounts of energy during radiative transitions, thereby allowing photons with a broader range of frequencies to produce a particular transition of a molecule.

What is threshold population inversion?

population inversion, in physics, the redistribution of atomic energy levels that takes place in a system so that laser or maser action can occur. Normally, a system of atoms is in temperature equilibrium and there are always more atoms in low energy states than in higher ones.

What causes line broadening?

In addition, there are three common causes of line broadening: natural, Doppler, and pressure broadening. Natural broadening and the Uncertainty Effect: Natural broadening of pure spectral lines occurs due to the finite amount of time an atom spends in its excited electronic state.

Why does line broadening occur?

Opacity broadening Electromagnetic radiation emitted at a particular point in space can be reabsorbed as it travels through space. This absorption depends on wavelength. The line is broadened because the photons at the line center have a greater reabsorption probability than the photons at the line wings.

What does line broadening tell us about a star?

If a star is rotating rapidly, there will be a greater spread of Doppler shifts and all its spectral lines should be quite broad. In fact, astronomers call this effect line broadening, and the amount of broadening can tell us the speed at which the star rotates (Figure 6).