Observation of thea 3Σ u + -X 1Σ g /+ system of calcium dimer

We report the observation of collision-induced spectra of calcium dimer in the 680–692 nm region. The spectra were recorded after resonant laser excitation of 4s4p 3 P 1 state of atomic calcium. Here the upper statea 3Σ u + is populated through collisions. The same spectra were reproduced in a low-current glow discharge in calcium vapor. The assignment of the observed spectral lines was carried out by applying the Dunham-type analysis and the spectra were assigned to thea 3Σ u + -X 1Σ g /+ transition of Ca2. The existence ofa 3Σ u + state withν 00 = 13850 ± 1 cm−1 andω e ∼ 37.6 cm−1 is confirmed.