A novel spectroscopic technique involving amplified spontaneous emission (ASE) is presented to excite single rotational levels of the 6s sigma T (2)Sigma (+) and 7s sigma Z (2)Sigma(+) Rydberg states of the NO molecule. In this excitation regime, the 3p pi D (2)Sigma(+) state, which is populated by the ASE deexcitation process from the 4s sigma E (2)Sigma(+) Rydberg state, serves as the intermediate state. As the initial radiative decay channels form the T (2)Sigma(+) and Z (2)Sigma(+) states, the dipole allowed ASE transitions down to the nearest Rydberg states, i.e., T (2)Sigma(+)-->5p sigma R (2)Sigma(+) and Z (2)Sigma(+ __)> 6p sigma Y (2)Sigma(+), are identified. The anomalous intensity distributions both in the excitation and emission spectra are well explained by s-d mixing and I uncoupling in the upper Rydberg states.