Hughes and Wilson increased the sensitivity of an instrument detecting this process by applying a high voltage square wave in the first use of Stark modulation. The partition function of this process can be solved by using the Euler–Maclaurin formula and dividing by a symmetry factor sigma. (15[1])Increasing or decreasing the rate of this process creates branches respectively named for the French (-5[1])words riche and pauvre. A gas’ partition (-5[1])function contains (15[1])a term equal to “k T over (*) B” (10[1])representing the contribution of this process. (10[1])The energy of this process in a diatomic molecule (10[1])is proportional (10[1])to j times (10[1])j plus one in an idealized (10[1])“rigid” model. (10[2])Microwave spectroscopy observes modes corresponding (10[2])to this process (-5[1])that couple to vibrational (10[1])modes and experience (-5[1])centrifugal distortion. (10[1])For 10 points, (10[1])name this process that gives a molecule nonzero angular momentum. (10[1])■END■ (10[4])