Abstract
A new (2+1) resonantly enhanced multiphoton ionization (REMPI) process via the a1Σ+g state of N2 with a quantum specific detection sensitivity of ∼105 molecule cm−3 is reported. The resulting spectra are easily analyzed and yield directly the relative rotational and vibrational populations in the ground electronic state of N2. Additionally, both two‐photon direct absorption (TPDA) to, and laser‐induced fluorescence (LIF) from two‐photon excitation of, the a‘ state of N2 are observed. These spectroscopies are compared with (2+1) REMPI and TPDA via the E,F state of H2.