Emission Spectrum of the PO Molecule. Part II.²Σ–²Σ Transitions

Abstract

Rotational structure of emission bands of the PO molecule in the region 5300-3800 A is analyzed.The spectrum is attributed to 5 electronic transitions A2Z+-B2Z+, F2Z+-B2Z+, G 2 Z + -B 2 Z + , H 2 Z + -B 2 Z + , and I 2 Z + -B 2 Z + , where F, G , H , and I are the new electronic states and A and B are the upper states of the well-known y and B bands respectively. Practically all the new ' Z states are found to be perturbed. A qualitative account of these perturbations together with a deperturbation of certain levels is given. A number of cases of predissociation are also observed. This predissociation is attributed to the presence of 411, and A"Z+ states, which dissociate to the ground state atomic products. From this an upper limit of the dissociation energy of the ground state of PO is determined to be Do = 49 536 cm-'. The A, D, E, G, H , and I states of this molecule are assigned as Rydberg states corresponding to the 04s, n4p, 63d, 04p, 03d, and 05s orbitals, respectively. From them a value of 67 570 cm-' is evaluated for the first ionization potential of PO. All the electronic states established for this molecule are described in terms of electron configurations.La structure de rotation des bandes d'emission de la molCcule PO, dans la region spectrale allant de 5300 a 3800 A a CtC analysee. Le spectre est attribue a 5 transitionselectroniques A2Z+-B2Z+, F 2 Z + -B 2 Z + , G2Z+-B2Z+, H2Z+-B2Z+ and 12Z+-B2Z+, ob F, G , H , et I sont les nouveaux Ctats electroniques, et oh A et B sont les niveaux superieurs des bandes bien connues y et B. Presque tous les nouveaux etats ' 2 apparaissent comme etant perturbes. On donne une explication qualitative de ces perturbations et du fait que certains niveaux ne sont pas perturbes. Un certain nombre de cas de predissociation sont aussi observes. Cette predissociation est attribute a la presence d'etats 411, et A J 2 Z + , lesquels se dissocient en atomes dans I'etat fondamental. Ce qui donne, comme limite superie~~re de l'energie de dissociation de I'etat fondamental de la molecule de PO, Do = 49 536 cm-'. Les etats A, D, E, G , H et I de cette molecule sont identifies cornme etats de Rydberg correspondant aux orbitales 04s, n4p, 63d, 04p, 0 3 d e t 0 5 4 respectivement. De ces orbitales une valeur de 67 570 cm-' est deduite pour le premier potentiel d'ionisation de la molecule de PO. Tous les etats electroniques etablis pour cette molecule sont dtcrits en termes des configurations electroniques.

Electronic spectra of diatomic oxides of Group VA elements

“…The existence of a 4rti state in PO similar to the 4ITi state of NO had been proposed by Couet et al, 31 Verma et al,12 and by Roche and Levebvre-Brion30 as the state responsible for the predissociations observed in the D2nr and B'2!! ; states.…”

“…On the basis of the molecular constants for this state (in PO) estimated in analogy with the corresponding values of NO, it is concluded that these perturbations are due to the v = 16 level of the 4n; state. An approximate potential energy curve for this state has been given by Verma et al 12 and the molecular constants are summarized in Table IV.…”

Multireference configuration interaction study on spectroscopic parameters and molecular constants of PO and PO+

“…The PO and PO + have been investigated extensively in experiment3–38. Further related references are given in many of the references cited here.…”

“…Henceforth, the PO radical became the subject of considerable work, and the spectroscopic properties were widely studied by emission and absorption spectroscopy, laser photoelectron spectroscopy, infrared (IR) spectra, and so on. In the 1960s and 1970s, much progress was achieved by Verma et al12–21 and Coquart et al22–28. Their studies led to the discovery of 22 electronic states and a considerable number of transition bands were observed amongst these states.…”