[2+1] Resonance enhanced multiphoton ionization reaction of diatomic halides ($I_2,Br_2,IBr$)

Abstract

The spectra of $I_2$, IBr, $Br_2$ have been studied in the wavelength range of 170 -174, 172.4 -176 and 264 -267 nm, using (2+1) resonance enhanced multiphoton ionization technique with time of flight mass spectrometer. The coupling between [3/2]5d:2g Rydberg state and $D_{2g}$ ion-pair state of $I_2$ are reconfirmed. The spectrum of IBr $b_6(Π_1)$ Rydberg states are obtained by observing $I^{+}$, $Br^{+}$ and $IBr^{+}$. The peak intensity ratio ($I^{+}:Br^{+}:IBr^{+}=85: 12: 3$) shows that the $I^+$, $Br^+$ are produced by photodissociation of $IBr^+$. The ionization cross section ratio of $Br_2$ is reported to be : $σ_i(Br* 264.89 nm)$/$σ_i(Br 264.79 nm)=0.33$±0.05 and$ σ_i (Br* 266.67nm)$/$σ_i(Br 266.60 nm)=0.55±0.05$, respectively. The calculated branching ratio Br*/Br of $CF_2Br_2$ using $σ_i(Br* 264.89 nm)$/$σ_i(Br 264.79 nm)$ is found to be 0.09.