Abstract
The A 2π-X 2Σ+ system of BeF has been photographed in absorption at high resolution, and the rotational analysis of the 1-0, 0-0 and 0-1 bands has been completed. The results confirm earlier work that the A 2π state is inverted, although derived mainly from the configuration... σ2π4π. This conclusion is in agreement with recent molecular orbital calculations on BeF, and is to some extent confirmed by other experimental work on this molecule which is briefly discussed.