By detecting the peak to peak amplitude the first derivative of the absorption is measured.By using phase sensitive detection only signals with the same modulation (100 k Hz) are detected. Note field modulation is unique to continuous wave EPR measurements and spectra resulting from pulsed experiments are presented as absorption profiles.Choosing an appropriate coordinate system (say, x,y,z) allows one to "diagonalize" this tensor, thereby reducing the maximal number of its components from 9 to 3: g are the components of the magnetic field vector in the coordinate system (x,y,z); their magnitudes change as the field is rotated, so does the frequency of the resonance.For a large ensemble of randomly oriented spins, the EPR spectrum consists of three peaks of characteristic shape at frequencies g: the low-frequency peak is positive in first-derivative spectra, the high-frequency peak is negative, and the central peak is bipolar.Therefore, transitions from the lower to the higher level are more probable than the reverse, which is why there is a net absorption of energy.The sensitivity of the EPR method (i.e., the minimal number of detectable spins , the implication is that the ratio of the unpaired electron's spin magnetic moment to its angular momentum differs from the free-electron value.
This is not an indication of a security issue such as a virus or attack.Since an electron's spin magnetic moment is constant (approximately the Bohr magneton), then the electron must have gained or lost angular momentum through spin–orbit coupling.Because the mechanisms of spin–orbit coupling are well understood, the magnitude of the change gives information about the nature of the atomic or molecular orbital containing the unpaired electron.In practice, EPR samples consist of collections of many paramagnetic species, and not single isolated paramagnetic centers.
If the population of radicals is in thermodynamic equilibrium, its statistical distribution is described by the Maxwell–Boltzmann equation: ≈ 0.998, meaning that the upper energy level has a slightly smaller population than the lower one.
In general, the g factor is not a number but a second-rank tensor represented by 9 numbers arranged in a 3×3 matrix.