Molecule Types Linear Molecules

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Linear Molecule State

This contains the rotational constants and other information specific to each state within a linear molecule. Note that PGOPHER will calculate Hund's cases (a) and (b) exactly. Other cases can be handled, but typically require more work to set up. For Hund's case (c), for example it may make sense to treat the various components of a state separately, which is possible by setting up multiple copies of the state and making use of the OmegaSelect and/or ParitySelect settings. For example the two halves of a ²Π state can be treated separately by setting up two ²Π states, one with OmegaSelect = ½ and one with OmegaSelect = 3/2.

Settings

Colour	Colour - set to "None" to take value from elsewhere as explained in Determining Colours and J ranges.
`RveSelect`	Only include given rovibronic symmetry - for normal use set to 'all'
S	Electron Spin
Lambda	Electronic angular momentum - use Sigma-, Sigma+, Pi, Delta, Phi, Gamma, H, I or a numerical value
gerade	True for gerade (g) states, false for ungerade (u) states; ignored if the molecule is not symmetric as specified by the `Symmetric` setting for the molecule.
OmegaSelect	Set to `all` for normal use; set to a specific value to restrict the basis states to a specific value of Ω. Basis states with other values of Ω are deleted, which will typically change calculated energies. (If you just want to display selected transitions, use the transitions window.) Note that if OmegaSelect is used the F1/F2/F3 numbering and N assignment may not be consistent, particularly for versions before 8.0.326. This is because of the algorithm used to determine if the state is regular or inverted; the `OmegaOrder` setting below can be used to force the desired order.
`OmegaOrder`	This is only used in assigning N, Ω and F1/F2/F3... quantum numbers to final states, and the default (`Auto`) is sufficient for all but rather unusual calculations. Possible values are `Auto` (the default), `Regular` (implying energies are expected to increase with Ω) and `Inverted` (energies decrease with Ω). The algorithm for assigning quantum numbers assumes energies increase with N and F number, so this controls how Ω is matched to these. In addition, if `LimitSearch` is set (the default), the expected energy ordering is used to assign the N and F1/F2/F3... quantum numbers.

Parameters

Origin	State Origin.
Width	Linewidth (rotation independent) for state.
B	Rotational constant.	Rotation
A	Spin-orbit coupling constant.	Spin-Orbit
LambdaSS	Spin - spin coupling constant, λ (=1.5*ε).	Spin-Spin
o	Spin-spin coupling constant giving lambda doubling for Omega = 0 states.	Λ Doubling
theta	Higher Order Spin-Spin interaction (S>=2 only).	Spin-Spin
Gamma	Spin rotation coupling constant.	Spin-Rotation
p	Lambda doubling constant.	Λ Doubling
q	Lambda doubling constant.	Λ Doubling
D	Quartic centrifugal distortion.	Rotation
H	Sextic centrifugal distortion.	Rotation
L	J⁸ centrifugal distortion.	Rotation
M	J¹⁰ centrifugal distortion.	Rotation
PP	J¹² centrifugal distortion. (Not P to avoid confusion with p.)	Rotation
LambdaD	Centrifugal Distortion of λ.	Spin-Spin
LambdaH	J⁴ Centrifugal Distortion of λ.	Spin-Spin
oD	Centrifugal distortion of o for Π states. n for Δ states.	Λ Doubling
oH	J⁴ Centrifugal distortion of o for Π states. o for Δ states.	Λ Doubling
oL	J⁶ Centrifugal distortion of o for Π states only.	Λ Doubling
pD	Centrifugal distortion of p for Π states only.	Λ Doubling
pH	J⁶ Centrifugal distortion of p for Π states only.	Λ Doubling
pL	J⁸ Centrifugal distortion of p for Π states only.	Λ Doubling
qD	Centrifugal distortion of q for Π states only.	Λ Doubling
qH	J⁶ Centrifugal distortion of q for Π states only.	Λ Doubling
qL	J⁸ Centrifugal distortion of q for Π states only.	Λ Doubling
gammaD	Centrifugal distortion of gamma.	Spin-Rotation
gammaH	J⁶ Centrifugal distortion of gamma.	Spin-Rotation
gammaL	J⁸ Centrifugal distortion of gamma.	Spin-Rotation
`eta`	Additional spin orbit term for quartet and higher states	Spin-Orbit
`gammaS`	Additional spin rotation term for quartet and higher states	Spin-Orbit
AD	Centrifugal distortion of A.	Spin-Orbit
AH	J² Centrifugal distortion of A.	Spin-Orbit
AL	J⁴ Centrifugal distortion of A.	Spin-Orbit
AM	J⁶ Centrifugal distortion of A.	Spin-Orbit

Note that the lambda doubling is only implemented fully for Π states. A partial implementation is available for Δ states - see Λ type doubling for Δ and higher states, and any required terms can be added using perturbations.