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The red-degraded [12.7]5Δ–X5Δ (0–0) band of gas-phase vanadium fluoride at 789 nm has been recorded by laser excitation spectroscopy and represents only the second reported rotational analysis of an electronic transition of VF. A hollow cathode discharge source was employed, with laser-induced fluorescence detected via the [12.7]5Δ–X5Δ (0–1) band. All five main (∆Ω = 0) subbands were identified, each containing only P and R branches, as expected in a parallel (∆Λ = 0) transition. The upper state displays the effects of strong local perturbations. Molecular constants describing the X5Δ (v = 0 and 1) levels and the [12.7]5Δ (v = 0) level were determined from least-squares fits using an effective Hamiltonian written in a Hund’s case (a) basis. The equilibrium rotational constant of the ground state was determined to be Be = 0.38324(89) cm−1, which yields a molecular bond length of Re = 1.7829(21) Å.
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Molecular spectroscopy as a laboratory experiment: Measurement of important parameters of sodium diatomic molecules
We present an inexpensive sodium molecular spectroscopy experiment for use in an advanced undergraduate laboratory course in physics or chemistry. The molecules were excited predominantly from the ground X1Σg+(v″ = 15) state to the B1Πu(v′ = 6) state using a commercially available 532-nm broadband diode laser. The laser-induced molecular fluorescence was measured using a miniature fiber-coupled spectrometer at a resolution of 0.5 nm. The spectral peak assignments were done by comparing the observed spectrum with the calculated Franck–Condon values. Important molecular constants such as fundamental frequency, anharmonicity, bond strength, and dissociation energy of the ground electronic state were determined by using the Birge–Sponer extrapolation method. The presence of highly visible blue glowing molecules along the green laser beam creates an engaging laboratory experience. Emphasis is placed on students developing their understanding of the molecular structure, practicing molecular spectroscopic techniques, and applying knowledge of light–matter interactions to a physical system.
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- Award ID(s):
- 2309340
- PAR ID:
- 10514918
- Publisher / Repository:
- AIP Publishing
- Date Published:
- Journal Name:
- American Journal of Physics
- Volume:
- 91
- Issue:
- 12
- ISSN:
- 0002-9505
- Page Range / eLocation ID:
- 1015 to 1022
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1119/5.0123126
