Photodissociation dynamics of the LiF molecule: Two- and three-state descriptions

The photodissociation of the lithium fluoride molecule gathered much attention lately. Theoretical works treating this subject usually consider the $1{}^1\mathrm{\Sigma }^{+}$ and $2{}^1\mathrm{\Sigma }^{+}$ electronic states, which are coupled nonadiabatically. As a continuation of a previous work, we intend to highlight the importance of the $1{}^1\mathrm{\Pi }$ state by investigating the kinetic energy and angular distribution of the photofragments. Besides, our results pointed out the importance of the molecular rotation.

Figure 1

(a) The lowest three adiabatic potential energy curves of the LiF molecule and the nonadiabatic coupling term $\tau (R$) between the two $\mathrm{\Sigma }$ states (scale is on the right side). (b) The transition dipole moment functions between the different electronic states. (c) Permanent dipole moment functions of the three adiabatic electronic states.

Figure 2

Light-induced potential energy surfaces for the three-state (a), (c) and two-state (b), (d) models calculated for the highest driving field intensities $I_d=4\times {10}^{13}$ $\mathrm{W}/{\mathrm{cm}}^2$ considered in this work. (c), (d) Show a zoom of the LIPs presented on (a) and (b), respectively, and concentrating on the LIAC (LICI) and regions. The coloring reflects the diabatic states that make up the different points of the adiabatic surfaces: red, ${\mathrm{\Sigma }}_1$; blue, ${\mathrm{\Pi }}_1$; green, ${\mathrm{\Sigma }}_2$.

Figure 3

Kinetic energy release spectra of the photofragments for the considered driving field intensities (indicated on the right axis of each row). On all panels, red lines with $+$ symbols and blue lines with $\circ$ indicate the spectra obtained for the three-state calculations on the ${\mathrm{\Sigma }}_1$ and ${\mathrm{\Pi }}_1$ states, respectively. The green lines marked with $\times$ show the results of the two-state calculations. Broken black lines mark the spectra obtained without a driving field.

Figure 4

Angular distribution of the photofragments for the considered driving field intensities (indicated on the right axis of each row). The 1D and 2D results are represented with dashed and continuous red lines for the ${\mathrm{\Sigma }}_1$, while dashed and continuous blue lines with $\times$ and $\circ$ symbols for the ${\mathrm{\Pi }}_1$ electronic state.