Fluorescence, Phosphorescence, and Photoluminescence Spectroscopy

Fluorescence, phosphorescence, and photoluminescence occur when a sample is excited by absorbing photons and then emits them with a decay time that is characteristic of the sample environment. Fluorescence is a term used by chemists when the absorbing and emitting species is an atom or molecule. Phosphorescence is similar to fluorescence, except that the time between absorption and emission is much longer than in fluorescence. Photoluminescence is the term physicists use to describe the absorption and emission of light by things such as semiconductors and nanotubes. Regardless of the terminology, when samples absorb photons and then emit them at a different wavelength the resultant light can be dispersed by a spectrograph, the spectrum can be detected by a device such as a CCD, and information can be gleaned about the sample.

As illustrated in the diagram at right, fluorescence occurs when a chemical species absorbs a photon and is excited to a singlet electronic excited state, relaxes via non-radiative mechanisms, emits a lower-energy photon, and then transitions to the ground electronic state. In fluorescence, the time between absorption and emission is on the order of nanoseconds. The spectrum of the wavelengths emitted can be used to identify atoms and molecules, as well as to determine chemical structures. The intensity of the photons emitted can be used to determine the concentration of chemical species.


Since absorption is a requirement for the fluorescence process, molecules and functional groups that are strong UV-Vis absorbers can be strong fluorescers. For example, molecules with extended pi-electron systems, including aromatic and conjugated aromatic rings, make excellent fluorescers (known as fluorophores). In biology, fluorophores are attached to molecules such as proteins, are excited, and the resultant fluorescence used to image molecules and cells. Spectral analysis of this fluorescence can give chemical information about biological systems.





A near-infrared fluorescence spectrum of a collection of carbon nanotube
(spectrum courtesy of Dr. Daniel A. Heller, Memorial Sloane Kettering Cancer Center, NY).

Phosphorescence is similar to fluorescence except the time between photon absorption and emission is from seconds to hours rather than nanoseconds. Like fluorescence, phosphorescence begins with absorption by a photon and excitation to a singlet electronic state. Via a process called intersystem crossing, the singlet state couples to a triplet electronic excited state, which then gives off a photon and relaxes to the ground electronic state. Singlet-triplet coupling is “forbidden” (which is responsible for the time delay in phosphorescence compared to fluorescence). The amino acid tryptophan phosphoresces, so phosphorescence can be used to study proteins.

Photoluminescence is fluorescence as applied to semiconductors and other materials. Dispersing the photoluminescent light to form a spectrum can give information such as the purity of semiconductors and the structure of nanotubes.

PI Picks

Fluorescing samples typically produce enough photons for a standard silicon-based CCD to detect a spectrum. Since fluorescence peaks are inherently broad, high-resolution spectra are not necessarily needed to obtain useful data.

IsoPlane Imaging Spectrographs

  • Eliminates field astigmatism across the entire focal plane, giving spectra with improved spectral resolution AND signal-to-background ratio
  • Produces crisp, detailed images across the entire focal plane


Acton SpectraPro Monochromators & Spectrographs

  • Grating stabilization offers simple calibration
  • Optimized coatings for higher throughput -
  • Interchangeable grating turrets with a wide selection of gratings 



  • Lifetime vacuum guarantee for worry-free operation
  • Deep cooling without the need for liquid circulators
  • Up to 1000 spectra/sec data acquisition
  • Quantum efficiencies of more than 90% available with Princeton Instruments custom sensor chips


Application Notes

High-Sensitivity, Large-Format CCD Camera -Enable Multidimensional Characterization of Soil-Grown Root Systems
GLO-Roots employs luminescence-based reporters and a pair of Princeton Instruments back-illuminated CCD cameras to enable studies of root architecture and gene expression patterns in soil-grown, light-shielded roots. Custom-designed image analysis algorithms allow the spatial integration of soil properties, gene expression, and root system architecture traits.

ProEM<br>  EMCCD电子增益相机



IsoPlane<br>  成像型光谱仪



PIXIS <br> 成像型与光谱型相机



LightField <br> 科学成像及光谱分析软件



SpectraPro <br> C-T型光谱仪



PyLoN <br> 成像型与光谱型相机



PyLoN-IR <br> 线阵型InGaAs相机


此款一维线阵InGaAs相机提供了16bit 数值深度;最快的光谱速度和最低的系统读出噪音在业界领先。

全新:Sophia<br> 超低噪声CCD相机




特色产品 Fluorescence, Phosphorescence, and Photoluminescence Spectroscopy

IsoPlane<br>  成像型光谱仪