Variables and Constants

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Symbol Meaning
c speed of light (c = 299,792,458 m/s approx 3 x 106m/s)
ν frequency
h planck's constant (h = 6.62606896x 10-34 J s = 4.135667 x 10-15eV s)
λ wavelength (visible spectrum is 400-700nm)

Absorption and Emission

Symbol Meaning
ε extinction coefficient of a molecule
Φ quantum yield
Ψ wave function

EO Properties

Symbol Meaning
μ dipole moment (mu) measured in debyes
α linear polarizability (alpha)
β molecular first hyperpolarizability (microscopic) (beta)
γ molecular second hyperpolarizability (microscopic) (gamma)
cos3θ order parameter
δ Two-photon cross section measured in Goppert-Mayer units (GM), with 1 GM=1×10-50 cm4 s molecules−1 photon−1 >100gm is high.)
r Pockels coefficient or Linear Electo-optic Coefficient Pockels Effect r~ 10-12 – 1—10 m/V
r33 Electro-optic coefficient (chi 33)(FM= 1000 pm/V)
χ2 second-order nonlinear susceptibility (first order hyperpolarizability) (macroscopic)
χ3 third-order nonlinear susceptibility (second order hyperpolarizability) (macroscopic) (alpha)(FM= 6-7 x 10-21(m/V)2)
ε dielectric constant or relative static permittivity
M Transition dipole moment (measured in debyes)
N Number Density parameter
φfl Fluorescence Quantum Yield a ratio of photons absorbed over photons emitted
σ conductivity (measured in S (Siemens)/cm
t the electronic coupling, transfer integral or resonance integral
vπ half-wave driving voltage


Symbol Meaning
α material loss in dB/cm
d electrode separation
Γ optical electrical overlap
λ reorganization energy
μ charge mobility in cm2 / V s- a mobility >1 is considered good

see also Wikipedia Greek Letters in Science