Knowledge Bank

The electronic absorption spectrum of $A3\Pi 1\leftarrow X1\Sigma +$ system of IBr was measured using a titanium sapphire laser. A large number of lines with $(4\le \nu \prime \le 13)\leftarrow (2\le \nu \prime \prime \le 6)$ were assigned. The P- and R- branch lines split into doublets owing to the nuclear hyperfine coupling effect. The first-order perturbation of the nuclear quadrupole coupling effect was taken into consideration. Rotational parameters of $B\backslash nuf\prime ,q\nu \prime$ and $D\nu \prime$ of the A-state and $B\nu \prime \prime$ of the X-state were determined using the least-squares fitting procedure. The centrifugal distortion constants $D\nu \prime \prime$ were fixed to the values calculated by using $Dc$ and $\beta c$ [1] for the $I79Br$ and to those by $\omega e$, $Be$ and $\alpha e$[2] for the $I81Br$. The spectroscopic constants determined, e.g for the $\nu =6\prime \leftarrow 4\prime \prime$ series of $I79Br$, are $\nu 0=11983.1096(10),B\backslash nuf\prime =0.0039572(6),q\nu \prime =4.87(20)\times 10-6,D\nu \prime =2.488(6)\times 10-8$ and $B\nu \prime \prime =0.0559939(6)incm-1.$