The CasesΒΆ

The identified cases are described in the following section; some examples are given below. It should be noted that the rovibronic states of different electronic states of a molecule may be described using different cases. For example, the ground, X^2\Pi electronic state of NO may be described within the hunda case whereas the excited, A^2\Sigma^+ electronic state would be better described using the hundb case. The electronic state is identified by its single-letter spectroscopic symbol (X, A, a, B, etc.) There follows a list of the cases identified in version 0.3 of XSAMS with some examples:

  1. General case for arbitrary quantum numbers and symmetry (gen)
  2. Diatomic closed shell (dcs): CO, N_2, NO^+
  3. Hund’s case (a) diatomics (hunda): NO, OH [for low J]
  4. Hund’s case (b) diatomics (hundb): O_2, OH [for high J]
  5. Closed-shell, linear triatomic molecules (ltcs): CO_2, HCN
  6. Closed-shell, non-linear triatomic molecules (nltcs): H_2O
  7. Closed-shell, symmetric top molecules (stcs): NH_3, CH_3Cl
  8. Closed-shell, linear, polyatomic molecules (lpcs): C_2H_2
  9. Closed-shell, asymmetric top molecules (asymcs): C_2H_4
  10. Open-shell, asymmetric top molecules (asymos): CH_3O
  11. Closed-shell, spherical top molecules (sphcs): CH_4, SF_6
  12. Open-shell, spherical top molecules (sphos)
  13. Open-shell, linear triatomic molecules (ltos): CCH
  14. Open-shell, linear, polyatomic molecules (lpos): C_3H, C_{10}H
  15. Open-shell, non-linear triatomic molecules (nltos): HO_2, CH_2