High-resolution optogalvanic study of the c4(0) 1Π u, c' 5(0) 1Σ u+, and a″(0) 1Σ g+ Rydberg states of N 2
A new optogalvanic technique with an rf discharge was applied to a high-resolution study of the Rydberg states of N 2. The Ledbetter band, c4(0) 1Π u ← a″(0) 1Σ g+, and a new visible band, c' 5(0) 1Σ u+ ← a″(0) 1Σ g+, were studied at a Doppler-limited resolution of 0.05 cm -1. A Doppler-free method was also applied to resolve overlapped lines. Precise wavenumbers were determined for the rotational transitions of the two Rydberg bands. The rotational and the centrifugal constants for the lowest Rydberg state, a″(0) 1Σ g+, were determined to be B0 = 1.913748(42) cm -1 and D0 = 6.088(99) × 10 -6 cm -1, where the numbers in parentheses are the standard deviation and apply to the last digits.