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The millimeter/submillimeter-wave spectrum of the SiP radical (X 2 Π i ) has been recorded using direct absorption spectroscopy in the frequency range of 151–532 GHz. SiP was synthesized in an AC discharge from the reaction of SiH 4 and gas-phase phosphorus, in argon carrier gas. Both spin–orbit ladders were observed. Fifteen rotational transitions were measured originating in the Ω = 3/2 ladder, and twelve in the Ω = 1/2 substate, each exhibiting lambda doubling and, at lower frequencies, hyperfine interactions from the phosphorus nuclear spin of I = 1/2. The lambda-doublets in the Ω = 1/2 levels appeared to be perturbed at higher J, with the f component deviating from the predicted pattern, likely due to interactions with the nearby excited A 2 Σ + electronic state, where ΔE Π-Σ ∼ 430 cm −1 . The data were analyzed using a Hund’s case a β Hamiltonian and rotational, spin–orbit, lambda-doubling, and hyperfine parameters were determined. A 2 Π/ 2 Σ deperturbation analysis was also performed, considering spin–orbit, spin-electronic, and L-uncoupling interactions. Although SiP is clearly not a hydride, the deperturbed parameters derived suggest that the pure precession hypothesis may be useful in assessing the 2 Π/ 2 Σ interaction. Interpretation of the Fermi contact term, b F , the spin-dipolar constant, c, and the nuclear spin-orbital parameter, a, indicates that the orbital of the unpaired electron is chiefly p π in character. The bond length in the v = 0 level was found to be r 0 = 2.076 Å, suggestive of a double bond between the silicon and phosphorus atoms.
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A new electronic transition of vanadium hydride: The C′5Δ–X5Δ (1,0) band
We report the observation and analysis of a new electronic transition in gas-phase vanadium hydride (VH), identified as the C′5Δ–X5Δ (1,0) band with an origin at 14,015 cm− 1 (714 nm). The spectrum was recorded by laser excitation spectroscopy, with laser-induced fluorescence detected to the X5Δ (v =1) level. Dispersed fluorescence measurements enabled a detailed characterization of the vibrationally excited ground state, yielding a vibrational interval of ΔG1/2 = 1606.6(2) cm− 1 . Despite the presence of significant local perturbations—particularly in the Ω =0 and 1 spin components of the C′5Δ state—a full rotational analysis of the spectrum using a Hund’s case (a) Hamiltonian was achieved. Spectroscopic constants including rotational, spin–orbit, spin–rotation, and Λ-doubling parameters are reported for both the new C′5Δ state and the X5Δ (v = 1) level. Additionally, we observed a small local perturbation in the X5Δ₁ (v =1) level near J =9, attributed to homogeneous spin–orbit and heterogeneous L-uncoupling interactions with the previously analyzed A5Π (v =0) state. An X5Δ ~ A5Π coupled Hamiltonian was used to model this perturbation and yielded interaction parameters roughly consistent with semi-empirical estimates. This work represents only the second analyzed spectroscopic transition of gas-phase VH.
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- Award ID(s):
- 2100542
- PAR ID:
- 10648775
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of molecular spectroscopy
- ISSN:
- 0022-2852
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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