Search results for "Overtone"
showing 10 items of 34 documents
A combined theoretical and experimental determination of the electronic spectrum of acetone
1996
A combined ab initio and experimental investigation has been performed of the main features of the electronic spectrum of acetone. Vertical transition energies have been calculated from the ground to the ny→π∗, π→π∗, σ→π∗, and the n=3 Rydberg states. In addition, the 1A1 energy surfaces have been studied as functions of the CO bond length. The 1A1 3p and 3d states were found to be heavily perturbed by the π→π∗ state. Resonant multiphoton ionization and polarization‐selected photoacoustic spectra of acetone have been measured and observed transitions were assigned on internal criteria. The calculated vertical transition energies to the ny→π∗ and all Rydberg states were found to be in agreeme…
Analysis of the rovibrational spectrum of 13CH4 in the Octad range
2013
Abstract We have measured the infrared spectrum of methane 13 CH 4 from 1100 cm −1 (33 THz), below the fundamental range, to about 12 000 cm −1 (360 THz) in the high overtone region at temperatures ranging from 80 K to 300 K by high resolution Fourier transform infrared (FTIR) spectroscopy. With instrumental bandwidths between 0.0027 cm −1 (80 MHz) and 0.01 cm −1 (300 MHz) this provides close to Doppler-limited spectra, using the Zurich prototype spectrometer (ZP2001, Bruker 125HR) combined with a multipath collisional cooling cell. Using perturbation theory and an accurate empirically adjusted potential we have computed ro-vibrational energy levels of 13 CH 4 and 12 CH 4 in the same energy…
Rovibrational Interactions in the Local-Mode Limit: The (n000) Stretching Overtone Bands of Spherical Tops
1995
Abstract We present a tensorial formalism adapted to the study of the ( n 000) rovibrational stretching states of spherical tops in the local mode limit. A local symmetrized rovibrational basis is built to take explicitly into account the fact that, in these states, the local symmetry is C 3ν rather than T d . Likewise, we introduce local rovibrational operators to build an effective Hamiltonian for these states. We then test our model by fitting the energy levels of 28 SiH 4 for 3 ≤ n ≤ 5.
Constraining properties of high-density matter in neutron stars with magneto-elastic oscillations
2017
We discuss torsional oscillations of highly magnetised neutron stars (magnetars) using two-dimensional, magneto-elastic-hydrodynamical simulations. Our model is able to explain both the low- and high-frequency quasi-periodic oscillations (QPOs) observed in magnetars. The analysis of these oscillations provides constraints on the breakout magnetic-field strength, on the fundamental QPO frequency, and on the frequency of a particularly excited overtone. More importantly, we show how to use this information to generically constraint properties of high-density matter in neutron stars, employing Bayesian analysis. In spite of current uncertainties and computational approximations, our model-depe…
High resolution study of the 3ν1 band of SO2
2009
Abstract The second overtone band 3 ν 1 of sulfur dioxide has been studied for the first time with high resolution rotation-vibration spectroscopy. About 3000 transitions involving about 900 upper state energy levels with J max. = 66 and K a max. = 24 have been assigned to the 3 ν 1 band. In the analysis, an effective Hamiltonian taking into account accidental interactions between the vibrational states (3 0 0), (2 2 0), and (0 4 1) was used. The Watson operator in A -reduction and I r representation was used in the diagonal blocks of the Hamiltonian. As the result of analysis a set of parameters reproducing the initial experimental data with the rms = 0.00028 cm −1 was obtained.
Hyperfine transitions in the first overtone mode of hydrogen deuteride
2020
Beyond the metrology and computational challenges associated with molecular hydrogen, key data are expected to assess the physics of simple molecular systems, and even the new physics beyond the standard model. To assist the deciphering of Doppler-free spectra obtained at very high accuracy ($\ensuremath{\sim}{10}^{\ensuremath{-}9})$, we report on hyperfine transitions of HD in the lowest vibrational levels of the ground electronic state. Using the spin-rotation, nuclear spin-spin, and quadrupolar hyperfine couplings determined by means of high-level quantum-chemical calculations, the hyperfine energy levels and the associated line intensity have been obtained by using tensorial momentum al…
2nu3 band of 12CF4 and its simultaneous analysis with nu3
1995
Abstract A nearly Doppler-limited spectrum of the 2ν 3 band of the 12 CF 4 molecule between 2536.0 and 2599.8 cm −1 was recorded at T = 77 K using difference-frequency laser spectroscopy. The simultaneous analysis of the ground (G.S.), ν 3 = 1, and ν 3 = 2 states was performed using an isolated band model to sixth order in the tetrahedral formalism. Fourteen hundred seventy-five transitions were assigned through J = 35 to the F 2 and E vibrational components of the ν 3 = 2 level. A total of 1864 transition frequencies were fit simultaneously (1000 2ν 3 - G.S. newly assigned transitions together with 575 ν 3 - G.S. and 289 ν 3 - ν 3 transitions already reported in the literature). The ground…
Internal Rotation in Propionic Acid: Near-Infrared-Induced Isomerization in Solid Argon
2005
The conformational system of propionic acid (CH3CH2COOH) is studied in solid argon. It is predicted by the ab initio calculations that this molecule has four stable conformers. These four structures are denoted Tt, Tg+/-, Ct, and Cg+/-, and they differ by the arrangement around the C-O and Calpha-C bonds. The ground-state Tt conformer is the only form present at 8 K after deposition of an argon matrix containing propionic acid. For the CH3CH2COOH and CH3CH2COOD isotopologues, narrow-band excitation of the first hydroxyl stretching overtone of the conformational ground state promotes the Calpha-C and C-O internal rotations producing the Tg+/- and Ct conformers, respectively. A subsequent vib…
Theoretical investigations of the IR spectroscopy of Ni(C(2)S(2)H(2))(2). A case study of the P_VMWCI(2) algorithm including anharmonic effects.
2010
The near infrared (NIR) spectra of bis(ethylene-1,2-dithiolato)nickel, Ni(C(2)S(2)H(2))(2) are fully interpreted here by applying a method developed for efficient automatic computation of both the infrared wave numbers and the intensities. The employed procedure uses parallel variational multiple window configuration interaction wave functions, the so-named P_VMWCI(2) algorithm, which incorporates both the mechanical and the electric anharmonic effects. It is shown that inclusion of anharmonicities is crucial for correctly assigning the fundamental, combination, and overtone vibrational frequencies in the infrared spectrum of the target system, for which conflicting assignments are found in…
Rotational Isomerism in Acetic Acid: The First Experimental Observation of the High-Energy Conformer
2003
The high-energy conformer of acetic acid (cis-AA) is produced in an Ar matrix by vibrational excitation of the OH stretching overtone of the ground conformational state (trans-AA). IR-absorption spectroscopy provides a clear identification of the reaction product. cis-AA converts back to trans-AA in a time scale of minutes at 8 K by tunneling. http://dx.doi.org/10.1021/ja038341a