Machine learning (ML) is transforming all areas of science. The complex and time-consuming calculations in molecular simulations are particularly suitable for an ML revolution have already been profoundly affected by the application existing ...Read More

The vibrational and K-type rotational levels of the [Xtilde] 2 B 1 Ã A states NH2 H2O+ have been fitted by least squares to give sets Born-Oppenheimer potential curves for combining electronic states. model used allows a simultaneous fit all observed vibronic each two molecules, using large amplitude formalism making no approximations other than neglect Fermi (anharmonic) resonance effects. An accurate description effects orbital angular momentum on level positions in molecules has obtained,...

A general method is described for calculating the vibronic energy levels associated with two Born-Oppenheimer states of a triatomic molecule that become degenerate in linear limit. The combines Renner's matrix treatment orbital angular momentum molecules Hougen, Bunker and Johns' formalism large amplitude bending motions, allows effects electron spins; it applies equally well to bent molecules. non-integral nature elements Lz are included, calculation relative band intensities optical...

A new transient absorption spectrum, attributed to the CCN free radical, has been discovered in flash photolysis of diazoacetonitrile, HC(CN)N 2 ; three electronic transitions, between 3 500 Å and 4 700 Å, have photographed for both CC 14 N 15 N. The ground state radical is a Π r state, excited states observed are Δ, B Σ − , C + . Δ show evidence Renner–Teller interaction vibrational angular momenta, an effect not previously states. Theoretical expressions energy levels linear triatomic...

The strongest features of the gas-phase absorption spectrum CS 2 in region 2900–3300 Å (Kleman's V system) are shown to belong a 1 B – Σ g + transition, where state correlates with upper Renner–Teller component π → π* Δ u linear molecule. barrier linearity is about 1300 cm −1 , and structure molecule zero-point level r(C–S) = 1.544 ± 0.006 Å, [Formula: see text]. Transitions lower component, A ( ), have been identified 3340–3500 Å: these consist progression vibronic Δ–Δ bands weaker Π–Π...

We report of the first gas-phase electronic spectrum V2. The dimer was generated in an expansion cooled molecular beam by laser vaporization vanadium metal. Using technique resonant two photon ionization spectroscopy a strong band system with origin near 7000 Å observed. Rotationally resolved spectra this conclusively demonstrate that transition is type 3Πu(a)←3Σ−g(a), and we assign 3Σ−g state as ground short bond length re″=1.77 high vibrational frequency ωe″=535 cm−1 are indicative...

A new transient absorption spectrum, belonging to the HCF free radical, has been discovered in flash photolysis of dibromofluoromethane, HCFBr 2 . The spectrum consists a single progression complex bands region 4 300–6 000 Å. Rotational analysis less severely perturbed shows them be type-C molecule that is nonlinear both upper and lower states transition, with bond angles ~ 127° 102° respectively. Axis-switching effects, due large change angle cause appearance prominent g Q, q ° Q branches,...

A long progression of absorption bands appearing in the region 5 500–8 200 Å has been observed flash photolysis dibromochloromethane, HCClBr 2 . Observation chlorine and deuterium isotope shifts, together with results rotational analyses, have shown that carrier is chloromethylene radical, HCCl.The ground state HCCl a 1 A′ which molecule an equilibrium angle ~103°, C—H bond length 1.12 Å, C—Cl 1.69 Å. In upper state, character A″, unusual patterns vibrational K-type energy levels indicate...

The A 3 Πi–X Σ − emission systems of OH + and OD have been reinvestigated in detail. Fourteen bands analyzed (of which seven are new), accurate rotational constants obtained for the levels ν = 0–2 two states 0–3 . Corrected assignments given low J lines (which important astrophysical spectra, such as those H 2 O containing comets).The perturbations Π both isotopes studied quantitatively, erratic Λ doubling explained position perturbing b 1 state has determined to within a few cm −1 , minor...

The vibrational structures of the 1744 Å Rydberg transitions C 2 H 4 and D have been examined in detail. For both isotopes relative intensities principal bands measured, various 'hot' appearing high temperature spectra assigned. Vibrational analysis has shown that ethylene molecule is non-planar at equilibrium 1 B 3(u) upper electronic state, being twisted by 25° ± 1°, with a potential barrier 290 20 cm −1 to inversion through planar configuration. C–C bond length state 1.41 0.01 hydrogen...

Rotational analyses have been carried out, with varying degrees of completeness, for nine bands S 16 O 2 and two 18 in the region 3000–3300 Å. The are all highly perturbed type C bands, which go to b vibrational levels ππ* Ã 1 A electronic state. [Formula: see text] transition shows an anomalous intensity distribution, indicates that state undergoes strong Born–Oppenheimer (nuclear momentum) vibronic coupling All obvious banded structure this wavelength can be assigned transition. Although...

Five bands of the à 2Π←X̃ 2Σ+ lowest electronic transition C2H have been observed in region 3600–4200 cm−1 an argon discharge over polyacetylene using color center laser spectroscopy with magnetic rotation sensitivity enhancement. The band origins are approximately 3692, 3773, 3785, 4011, and 4106 cm−1. Rotational assignments preliminary fittings all five made. Four a lower vibronic state which is undoubtedly ground molecule, different 2Π upper states correspond to mixtures three...

Precise frequencies for the observed lines of five bands à 2Π ← X̃ 2Σ system C2H are reported. These have been least-squares fitted with an effective rotational Hamiltonian and resulting parameters given.

The electronic orbital angular momentum effects in the à 1II u state of C3 have been considered. A very good fit to observed vibronic energy levels and rotational constants has obtained using a full matrix treatment conjunction with large amplitude formalism for bending motion. importance variation expectation value <Lz > bond angle is emphasized; quality final much improved when this included. Franck-Condon overlap integrals calculated bands -[Xtilde] 1Σ g + transition, which carrier 4050 Å...

The effects of orbital angular momentum on the details spin and rotational fine structure [Xtilde] 2 B 1 Ã A states NH2 H2O+ are considered. It is found that erratic spin-orbit splittings asymmetry parameters can be reproduced with good accuracy by calculations also account for regular structures ground states; only input shapes Born-Oppenheimer potential curves, bond lengths coupling constants. same give an almost quantitative explanation various perturbations in state NH2. These caused...

Rotational analyses have been carried out for the three longest wavelength bands observable in '2900 Å system' of SO 2 (at 3340, 3359, and 3395 Å). Although are perturbed quite severely it has possible to prove that they type C bands, approximate upper state geometric structure molecule is r(S—O) = 1.53 Å, [Formula: see text]. Comparison with theoretical calculations Hillier Saunders now leaves little doubt electronic π → π* 1 A state, appearing absorption by Herzberg–Teller mixing through Q...

The flash photolysis of diazopropyne (HC 2 ∙CHN ) provides a particularly strong absorption spectrum the free C 3 radical. About 40 μs after flash, appearance [Formula: see text] (4 050 Å) system is similar to that obtained in diazomethane by Gausset, Herzberg, Lagerqvist, and Rosen, though much more intense. intensity has permitted study l-type doubling effect ground-state level 6ν , which component been found lie at 458.2 cm −1 . At shorter time delays complicated bands arising from levels...

The ultraviolet absorption spectrum of the free CNC radical has been discovered in flash photolysis diazoacetonitrile, HC(CN)N 2 . identity proved from isotopic evidence, using 15 N and 13 C, together with rotational analysis bands. Rotational analyses have shown that bands must be assigned to two electronic transitions, A Δ u –X Π g , [Formula: see text]. sequence bending vibrations, which are observed both show evidence Renner–Teller interaction degenerate states: this is extremely large X...

A. J. Merer, Discuss. Faraday Soc., 1963, 35, 127 DOI: 10.1039/DF9633500127