We report the results of initial FUSE observations of molecular hydrogen ( H _ { 2 } ) in translucent clouds .
These clouds have greater optical depth than any of the diffuse clouds previously observed for far-UV H _ { 2 } absorption , and provide new insights into the physics and chemistry of such regions .
Our initial results involve observations of HD 73882 , a well-studied southern hemisphere star lying behind substantial interstellar material ( E _ { B - V } = 0.72 ; A _ { V } = 2.44 ) .
We find a total H _ { 2 } column density , N ( H _ { 2 } ) = 1.2 \times 10 ^ { 21 } cm ^ { -2 } , about three times larger than the values for diffuse clouds previously measured in the far-UV .
The gas kinetic temperature indicated by the ratio N ( J =1 ) /N ( J =0 ) is 58 \pm 10 K. With the aid of ground-based data to calculate an appropriate multi-component curve of growth , we have determined column densities for all rotational levels up to J = 7 .
The J \geq 2 states can be reasonably fitted with a rotational excitation temperature of 307 \pm 23 K. Both the kinetic and rotational temperatures are similar to those found in previous investigations of diffuse clouds .
The ratios of carbonaceous molecules to hydrogen molecules are also similar to ratios in diffuse clouds , suggesting a similar chemistry for this line of sight .