Near-infrared diode laser spectroscopy of free radicals.
Spectroscopic results on the radicals HCSi, CCO, and FeC obtained by studying in detail energy level structures using 0.8 microm diode laser system are reported. Of these radicals, the CCO radical was investigated mainly using Fabry-Perot type diode lasers with inconvenient mode gaps in the early stage of our near-infrared diode laser spectroscopic study of free radicals, and on the other hand, the FeC and HCSi radicals were studied using an external cavity diode laser. For the FeC radical, which is an interesting radical composed of an iron atom having 3d electrons, information on spin-orbit interaction between the triplet electronic ground state and a low-lying singlet electronic excited state is reported somewhat in detail. For the HCSi and CCO radicals, spectral particularities produced by a Renner-Teller interaction and a spin-orbit interaction are described for their high-resolution spectroscopic interest.
Near-Infrared Diode Laser Spectroscopy of FeC in the 0.8-μm Region: A Simultaneous Analysis of the X3Δi and [3.8]1Δ States
Abstract The near-infrared absorption spectra of the FeC radical have been measured by diode laser spectroscopy in the regions from 11 810 to 13 200 cm −1 . Rotationally resolved 28 new vibronic bands of the 56 Fe 12 C major isotopic species were observed as well as two known bands. Five of them were assigned as the v ′= v ″=0–4 sequence bands in the [13.1] 3 Φ 4 ← X 3 Δ 3 system, six are the v ′= v ″=0–5 sequences in the [13.18]Ω=3← X 3 Δ 2 system, and five were assigned as the v ′= v ″=0–4 sequences in the [13.5]Ω=2← X 3 Δ 1 system. The X 3 Δ 1 state of FeC is reported for the first time but we found that the rotational constant for this state of 56 FeC is very close to that for the X 3 Δ 3 state of 54 FeC. Transitions of the 54 FeC minor isotopic species for the two known bands were thus reinvestigated. For the unclassified 11 new bands, the lower states were assigned as the v =0–3 states in X 3 Δ i . The energy difference between the Ω=2 and 3 sublevels in the X 3 Δ i state could be determined to be 329.8059±0.0005 cm −1 as a results of the analysis of the two of new bands, [12.32]← X 3 Δ 3 v =0 and [12.32]← X 3 Δ 2 v =0 observed near 12 317 cm −1 and 11 987 cm −1 , respectively. Stimulated emission pumping spectra were also recorded near 17 600 cm −1 to examine the low-lying electronic state which had been observed 3460 cm −1 above the X 3 Δ 2 state (K. Aiuchi and K. Tsuji and K. Shibuya, Chem. Phys. Lett. 309, 229–233 (1999)), and it was assigned as the [3.8] 1 Δ state arising from the same configuration as that of X 3 Δ i (…3π 4 1δ 3 9σ 1 ). In addition, the v =0–0 and 1–1 bands of the [16.2]Ω=3←[3.8] 1 Δ system were observed by near-infrared diode laser spectroscopy. The lower state combination differences were calculated for the possible sets of the energy levels in the X 3 Δ i and [3.8] 1 Δ states with v =0–5 by using the present result and the other spectroscopic data reported. A simultaneous analysis was carried out by using the combination differences to determine the molecular constants for the X 3 Δ i and [3.8] 1 Δ states as well as the off-diagonal spin–orbit interaction terms. The [13.18]Ω=3 state and the [13.5]Ω=2 state were concluded to be other two spin sublevels for the [13.1] 3 Φ 4 state and the [16.2]Ω=3 state was assigned as an isoconfigurational 1 Φ state.
Fourier-transform infrared spectroscopy of the NO3 radical
Abstract The infrared spectrum of NO 3 was observed in the 1300–2800 cm −1 region by a high-resolution FT-IR spectrometer using the reaction of F atoms with HNO 3 . Three 2 E′- 2 A′ 2 bands were newly observed in the 1927, 2024, and 2155 cm −1 region in addition to the 1492, 2518, and 2585 cm −1 bands observed previously by a diode-laser system. The 2024 and 2155 cm −1 bands were analyzed by using a D 3h Hamiltonian to derive molecular constants. It was found that the obtained spin—orbit and Coriolis coupling constants in the 2 E′ states are very different for different vibronic states. The vibronic assignments of these bands are discussed.