Geometrical Structure. Vibrations. Dissociation

The ground state bending frequency V2(Ai) may be -1200 cm a characteristic separation between different bands In the predissociation spectrum of the A Ai transition (see 

Theoretical geometrical and vibrational data from HF calculations [1, 5] are given below (internuclear distance r in A fundamental vibrations Vj in cm almost identical values are in [6])  

Geometrical parameters for both states were also calculated (HF and complete active space (CAS) SCF) in [7], for both states and A (GVB) in [8]. A bond angle for X Ai was calculated (CNDO/2) in [9]. Geometrical parameters and force constants from earlier MO-SCF calculations [10] are for a state (supposedly the ground state). 

Dissociation. Electronic states of the dissociation products P + H2, PH + H, and PH + H have been correlated with states of PHJ in [11 ] (in a figure of bending potential energy curves). 

---

The application of both criteria to gas-phase reactions is complicated further by the formation of vibrationally excited products. Both the insertion and addition reactions of methylene are exothermic by approximately 93 kcal. mole (based on recent estimates of AH (CH2) = 94 kcal.mole" ). Vibrationally excited alkanes and alkenes may dissociate into free radicals, and excited cyclopropanes may undergo structural and geometrical isomerizations unless collisionally stabilized . The occurrence of hot molecule reactions excludes any reasonable estimation of singlet and triplet methylene fractions. The data presented in the following paragraphs have been taken from experiments at high-pressures", which are thought to ensure complete collisional deactivation of excited reaction products. 

---