Molecule Types Vibrational Structure Vibrational Energy Levels and Franck-Condon Factors <Prev Next>

Vibrational Mode

One of these items will be present for each vibrational mode under each electronic state. The number is controlled by the nModes at the molecule level.

Settings

Symmetry Symmetry of this vibrational mode. Note that this setting is shared with every state in the molecule.
vMin Minimum vibrational quantum number for this mode to include in the basis. Note that an implementation restriction in the current version means that values of vMin > 0 are likely to slow calculations for intensities considerably.
vMax Maximum vibrational quantum number for this mode to include in the basis. Note that in more recent versions of the program the default for this is 3 if there are 3 or less vibrational modes, otherwise 0. This avoids asking for very large calculations by accident; if the product over all modes of (vMax+1) is more than 50 or so the calculation is likely to become rather slow.

Parameters

Omega Vibrational Frequency
xOmega Anharmonic terms. The diagonal vibrational energy is taken as:
Omega(v+d/2) + xOmega(v+d/2)2 + yOmega(v+d/2)3 + zOmega(v+d/2)4 + gll2
where d is the degeneracy of the mode. Note the sign of xOmega - this is often taken as negative in the Dunham expansion for diatomic molecules. For polyatomic molecules, xOmega is typically written as xii, yOmega as xiii and zOmega as xiiii. For terms involving more than one mode, such as x12, add a Vibrational Perturbation.
yOmega
zOmega
gll
epsOmega Renner-Teller term. The operator multiplying this is q+2|Λ|e−2i|Λ|φ + q−2|Λ|e+2i|Λ|φ, with the e∓2i|Λ|φ term imposing a ΔΛ = −Δl = ±|Λ| selection rule. For Π states the term used in the literature is often ½εω(q+2e−2iφ+q−2e+2iφ), so the value required here may be half that quoted in the literature.
lx0 Elements of the matrix M-½ l for the first nucleus for this vibrational mode in units of 1/sqrt(amu). Repeated  for each nucleus, or absent if the l matrix is not being used.
ly0
lz0
...

Operations

Right click on the item in the constants window for the following operations in addition to the standard ones:

Sort Sort modes into standard order, i.e. Symmetry and then descending order of frequency. Note that this option re-orders the modes in every state of the molecule.
Global Shift Up Shift this mode up in every state in the molecule. Note that the "Move Up" item on the same menu only moves the values up for the selected state.
Global Shift Down
 Shift this mode down in every state in the molecule. Note that the "Move Up" item on the same menu only moves the values up for the selected state