Wavenumber (Cm⁻¹)
Definition
The number of wavelengths per centimetre, equal to 1/λ when λ is in cm. The working unit of vibrational spectroscopy because it is directly proportional to energy and avoids the inconvenient powers of ten that nanometres and hertz introduce.
Related terms
- Band Spectrum
- A continuous-looking envelope of closely spaced lines produced by molecules. Electronic, vibrational and rotational transitions couple together so a single electronic excitation...
- Beer-Lambert Law
- A = εbc. Absorbance equals molar absorptivity times path length times concentration. The linear relation between absorbance and concentration that makes UV-Vis...
- Line Spectrum
- A discrete pattern of sharp lines produced by atoms in the gas phase. Each element has a unique line pattern set by...
- Quantised Energy Level
- An allowed state of an atom or molecule. Transitions between levels happen only at discrete energies set by the level spacing, not...
- Selection Rule
- A quantum-mechanical rule that decides whether a transition between two levels is allowed or forbidden. Allowed transitions are intense and fast; forbidden...
Explained in
- Atomic and Molecular Spectra FundamentalsThe number of wavelengths per centimetre, equal to 1/λ when λ is in cm. The working unit of vibrational spectroscopy because it is directly proportional to ene...