levelsplot

Display energy level diagram, resonances and stick spectrum.

Syntax

levelsplot(Sys,Ori,B)
levelsplot(Sys,Ori,B,mwFreq)
levelsplot(Sys,Ori,B,mwFreq,Opt)

Description

Displays the energy level diagram (Zeeman diagram) for the spin system specified in Sys. Ori specifies the magnetic field direction in the molecular frame. B gives the field range, and mwFreq provides the microwave frequency.

Ori can be either an array of numbers or a character array. As numeric array, it specifies the Euler angles [phi theta] or [phi theta chi] of the magnetic field relative to the molecular frame of the spin system. The three principal directions x, y, and z of the molecular frame, as well as a few specific intermediate orientations, can be specified by shorthands instead: 'x' for [0 pi/2], 'y' for [pi/2 pi/2], 'z' for [0 0], 'xy' for [pi/4 pi/2], 'xz' for [0 pi/4], 'yz' for [pi/2 pi/4], and 'xyz' for [pi/4 acos(1/sqrt(3))]. If Ori is omitted, 'z' is assumed by default.

B contains the magnetic field range, in mT. If it is an array with two numbers [Bmin Bmax], they are understood to be the lower and upper limit of the field range. If it is a single number, it is understood to be the upper field limit (Bmax), and the lower one is assumed to be zero. The number of field values between the two limits is set automatically, but can be modified via Opt.nPoints. If B is a full vector of field values, they are used directly.

If mwFreq, the spectrometer frequency in GHz is given, resonances for this frequency are plotted as well. Their color indicates the transition amplitude: Red lines indicated allowed resonances, gray ones indicate forbidden ones. Clicking on a resonance line will print its relative transition probability to the command window.

Hovering with the mouse pointer over an energy level displays its number, and hovering over a transition (if the microwave frequency was provided) will display the resonance field as well as the relative intensity of this transition, with 1 being the value for the most intense transition.

Opt is an optional structure to provide additional settings. It can have the following fields:

Units

Energy units for plotting. The possible values are 'GHz' (default), 'cm^-1', or 'eV'.

nPoints

Number of points along the field axis.

PlotThreshold

Transitions with relative intensity below this value will not be plotted.

SlopeColor

true or false (default). If set to true, energy level lines are colored according to the magnitude of their slope. This corresponds to the expectation value for |m_S| for the corresponding state. At anticrossings, this reveals that the state character changes rapidly as a function of field.

StickSpectrum

true or false. If true, a stick spectrum is plotted beneath the energy level diagram.

Examples

To plot resonances at X band for a spin center with S=5/2 and rhombic zero field splitting, use

clear
spins.S = 5/2;
spins.g = 2;
spins.D = [-250 -1750 2000];  % MHz
Ori = 'z';
FieldRange = [0 500];  % mT
mwFreq = 9.5;  % GHz
Opt.SlopeColor = true;
levelsplot(spins,Ori,FieldRange,mwFreq,Opt);

Algorithm

Energy levels are computed using levels. Resonances are computed using resfields.