Near infrared 3ν2 overtone band of H+3

Near infrared spectrum of the 3ν2 overtone band (ν2=3←0) of H+3 has been observed at 1.4 μm. The spectrum is weaker than the ν2 fundamental band by a factor of ∼250. High sensitivity plasma spectroscopy using velocity modulation and unidirectional multiple passing has enabled us to observe 15 rovibrational transitions. Short-external-cavity InGaAsP diodes were used as tunable near infrared radiation sources. The narrow tuning range and the availability of diodes limited the observation to a fraction of observable transitions. Nevertheless, the observed results provide information on the rovibrational energy of the 3ν2(l=1) state which may be used to further improve the variational calculations by Miller and Tennyson.