This paper describes a new spectroscopic technique which uses photodissociation to detect pure rotational transitions in highly excited vibrational energy levels of the ground electronic state. This method has initially been applied to the (HOCl)-Cl-35 molecule in its second excited OH stretching vibration, the (200) state. In addition to observing the microwave signal, the Stark effect for this transition provides a dipole moment measurement in the (200) vibrational state. The (200) 18(0,18) --> 17(1,17) transition occurs at 14 858.40(1) MHz and the b component of the dipole moment of this state is mu(b) = 1.515(5) D. The technique is quite general in that the rotational transition can involve energy levels up to, and exceeding, the dissociation threshold of the ground electronic state. (C) 1999 American Institute of Physics. [S0021-9606(99)00632-7].