Abstract. We have measured the reduced absorption coefficients occurring in the wings of the potassium 4²S–5²P doublet lines at 404.414 nm and at 404.720 nm broadened by helium gas at pressures of several hundred Torr. At the experimental temperature of 900 K, we have detected a shoulder-like broadening feature on the blue wing of the doublet which is relatively flat between 401.8 nm and 402.8 nm and which drops off rapidly for shorter wavelengths, corresponding to absorption from the X²Σ⁺ state to the C²Σ⁺ state of the K–He quasimolecule. The accurate measurements of the line profiles in the present work will sharply constrain future calculations of potential energy surfaces and transition dipole moments correlating to the asymptotes He–K(5p), He–K(5s), and He–K(3d).

Print publication: Issue 14 (28 July 2007)
Received 9 May 2007
Published 4 July 2007