What is the Difference Between Excitation and Absorption?
🆚 Go to Comparative Table 🆚The main difference between excitation and absorption lies in the processes they describe and the spectra they produce. Here are the key differences:
- Absorption:
- Absorption is the process of taking in energy, typically in the form of light, by an atom or molecule.
- An absorption spectrum shows all the wavelengths at which light is absorbed by a sample.
- Absorption spectra are measured using a UV-Vis spectrophotometer.
- Excitation:
- Excitation is the process of increasing the energy level of an atom or molecule.
- An excitation spectrum shows the wavelengths of light that a sample will absorb to be able to emit at a specified wavelength.
- Excitation spectra are measured using a fluorescence spectrophotometer.
These processes are interrelated in the context of fluorescence, where fluorophores absorb light energy at particular wavelengths (absorption), reach an excited state (excitation), and then emit light at longer wavelengths at a lower energy level (emission). Generally, both the absorption and excitation spectra of a fluorophore will have the same peak wavelength, although there are exceptions.
Comparative Table: Excitation vs Absorption
The main difference between excitation and absorption lies in the energy transfer processes involved. Here is a table summarizing the differences between the two:
| Property | Excitation | Absorption |
|---|---|---|
| Definition | Excitation is the process of increasing the energy level of an atom or molecule. | Absorption is the process of absorbing energy, typically from light, by a system. |
| Relationship | Excitation is followed by emission, which occurs when the system returns to a lower energy state. | Absorption is the initial step in this process, followed by excitation and then emission. |
| Spectroscopy | Excitation spectra are recorded for fluorescent materials along with their usual absorption spectra. | Absorption spectra (also known as UV-Vis spectra, absorbance spectra, and electronic spectra) show the change in absorbance of a sample as a function of wavelength. |
| Measurement | Excitation spectra can be thought of as fluorescence detected absorption spectra. | Emission spectra are measured by varying the wavelength of the excitation monochromator and recording the intensity of light transmitted through the sample. |
In summary, excitation is the process of increasing the energy level of a system, while absorption is the process of absorbing energy from an external source. Both processes are closely related and often occur sequentially in spectroscopic studies.
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- Absorption Spectrum vs Emission Spectrum
- Action Spectrum vs Absorption Spectrum
- Excitation vs Ionization Potential
- Neutron Capture vs Absorption
- Absorption vs Assimilation
- Digestion vs Absorption
- Atomic Absorption vs Atomic Emission
- Absorbance vs Fluorescence
- Excitation vs Emission Filter
- Absorption vs Stripping
- Absorptivity vs Molar Absorptivity
- Absorbance vs Transmittance
- Ground State vs Excited State
- Adsorption vs Desorption
- Molar Absorptivity vs Specific Absorbance
- Emission vs Radiation