This model demonstrates the attosecond transient absorption spectra computed using the following formula: $$ \sigma (\omega,\tau) = \frac{4\pi\omega}{c} \text{Im} \sum_I \sum_J c_I c_J \exp\left( i (E_I - E_J) \tau \right) \sum_F \langle \Phi_I | \hat{\mu} | \Phi_F \rangle \langle \Phi_F | \hat{\mu} | \Phi_J \rangle \left( \frac{1}{\tilde{E}_F - E_I - \omega} + \frac{1}{\tilde{E}^*_F - E_J + \omega} \right) $$ See these references for detailed discussion:
  1. R. Santra et al., Phys. Rev. A 83, 033405 (2011).
  2. N. Golubev et al., Phys. Rev. Lett. 127, 123001 (2021).

$$\langle \Phi_1 | \hat{\mu} | \Phi_{F_1} \rangle =$$

$$\langle \Phi_1 | \hat{\mu} | \Phi_{F_2} \rangle =$$

$$\langle \Phi_2 | \hat{\mu} | \Phi_{F_1} \rangle =$$

$$\langle \Phi_2 | \hat{\mu} | \Phi_{F_2} \rangle =$$

$$c^2_1 =$$