Introduction to Spectroscopy

Spectroscopy studies the interaction between electromagnetic radiation and matter, particularly focusing on how atoms and molecules absorb and emit light. This interaction provides valuable information about the composition and structure of materials.

Atomic Energy Levels and Electronic Transitions

Ground and Excited States

In the Bohr model of the atom, electrons occupy discrete energy levels around the nucleus. The lowest energy state is called the ground state, while higher energy states are excited states. The energy of each level ($E_n$) is given by:

$$E_n = -\frac{13.6\text{ eV}}{n^2}$$

Where n is the principal quantum number.

Electronic Excitation

When an atom absorbs energy equal to the difference between two energy levels, an electron can jump to a higher energy state:

$$\Delta E = E_2 - E_1 = hf$$

Where:

Electronic Relaxation

Excited electrons eventually return to lower energy states, releasing energy as electromagnetic radiation:

$$\lambda = \frac{hc}{\Delta E}$$

Where:

Types of Spectra

Continuous Spectra

White light passed through a prism produces a continuous spectrum containing all visible wavelengths. Incandescent objects, like tungsten filaments, also produce continuous spectra due to thermal radiation.

Absorption Spectra

When white light passes through a cool gas:

Emission Spectra

Hot gases emit light at specific wavelengths when electrons return to lower energy states:

Experimental Methods

Gas Discharge Tubes

Gas discharge tubes demonstrate emission spectra:

Components:

Solar Spectrum Analysis

The Sun's spectrum shows absorption lines due to:

Incandescent Sources

Incandescent lamps produce light through:

Key characteristics: