Spectroscopy 101: How Absorption and Emission Spectra Work

Introduction

Spectroscopy is used to analyze the composition of stars and nebulae by examining their absorption and emission spectra.
Every element has a unique spectrum, akin to a fingerprint.

Structure of Hydrogen Atom: One proton in the nucleus and one electron orbiting.
Electron Energy Levels:
- Electrons reside in specific energy levels.
- Absorption of light causes electrons to jump to higher energy levels.
- Energy levels are discrete; electrons can't exist between them.
- The energy required corresponds to the wavelength of absorbed light.
Hydrogen Absorption Spectrum:
- Specific wavelengths absorbed: 410 nm (violet), 434 nm (blue), 486 nm (blue-green), 656 nm (red).
- Each absorption line is linked to a specific electron jump.

Diagram: Shows electron jumps and corresponding wavelengths in the hydrogen absorption spectrum.
Key Concept: Shorter wavelengths cause larger energy jumps.

Electron Energy Loss:
- Electrons emit photons when dropping to lower energy levels.
- Emission spectrum mirrors the absorption spectrum.
Hydrogen Emission Spectrum:
- Emission lines at the same wavelengths: 410 nm, 434 nm, 486 nm, 656 nm.
- Farther electron drops emit shorter wavelength, higher energy light.

Emission Spectrum Components:
- Purple, blueish-purple, blue, and red lines represent emission spectrum.
- Peaks on a graph correlate with these emission lines and brightness.
Graph Representation:
- Shows peaks at specific wavelengths, increasing in height.

Different elements have unique spectra because of varying proton and electron configurations.
Molecules (e.g., water, CO2, methane) have complex spectra due to electron, rotation, and vibration changes.

Spectroscopy allows for the identification of elements and molecules by analyzing their unique spectra.