First rotational analysis of the A2Π-X2Π system of the P35Cl+ cation

The visible A2Π → X2Π band system of PCl+ has been recorded photoelectrically with a resolution of 0.006 nm. Fourteen 2Π1/2–2Π1/2 and six 2Π3/2–2Π3/2 sub-bands of P35Cl+ in the ν′ = 0 and 1 progressions with 10 ≤ ν″ ≤ 20 have been rotationally analysed. The measured positions of 1214 lines have been fitted directly by least squares to obtain a set of reliable constants for the two states that reproduce the entire data. These constants include the first estimated spin–orbit coupling constants for both states. The reliability of these estimates is discussed. The equilibrium internuclear separations are re(X) = 0.1900 and re(A) = 0.2334 nm.