  High Rydberg states of nitric oxide (NO) with principal quantum numbers
between 40 and 100 and lifetimes in excess of 10 $\mu$s have been prepared by
resonance enhanced two-color two-photon laser excitation from the X
$^2\Pi_{1/2}$ ground state through the A $^2\Sigma^+$ intermediate state.
Molecules in these long-lived Rydberg states were detected and characterized
126 $\mu$s after laser photoexcitation by state-selective pulsed electric field
ionization. The laser excitation and electric field ionization data were
combined to construct two-dimensional spectral maps. These maps were used to
identify the rotational states of the NO$^+$ ion core to which the observed
series of long-lived hydrogenic Rydberg states converge. The results presented
pave the way for Rydberg-Stark deceleration and electrostatic trapping
experiments with NO, which are expected to shed further light on the decay
dynamics of these long-lived excited states, and are of interest for studies of
ion-molecule reactions at low temperatures.
