The fluorescence spectrum of NO2: rotationally-forbidden bands and their interpretation

1977 ◽  
Vol 55 (16) ◽  
pp. 1453-1461 ◽  
Author(s):  
H. D. Bist ◽  
J. C. D. Brand ◽  
A. R. Hoy
Keyword(s):  
Excited State ◽  
Electronic State ◽  
Fluorescence Spectrum ◽  
Quantum Number ◽  
Ground State ◽  
Vibronic Coupling ◽  
Gas Pressure ◽  
Initial State ◽  
Final State ◽  
Vibrational Levels

Fluorescence of NO2 excited near 5000 Å at low gas pressure is predominantly 'parallel' in type, i.e., the values of the quantum number K in the initial state of the excitation, the intermediate (excited) state, and the final state(s)of the emission are all equal, Ki = K′ = Kf. However, a considerable number of the weaker fluorescence bands do not conform to this pattern; instead, they correspond to even-parity differences between the initial and final value of K, |Kf − Ki| = 2, 4, or 6, indicating that K (though not N) is a poor quantum number in the upper electronic state of the excitation–emission sequence. The observations are analyzed in terms of a mechanism in which the vibronic coupling between the 2B2 excited state and high vibrational levels of the ground state creates conditions where the asymmetry of the 2B2 basis state produces unexpectedly large couplings between hybrid states of the same parity in K.

Rotational Structure in the Absorption Spectrum of SO2 between 3000 Å and 3300 Å

1975 ◽  
Vol 53 (23) ◽  
pp. 2555-2576 ◽  
Author(s):  
Y. Hamada ◽  
A. J. Merer
Keyword(s):  
Absorption Spectrum ◽  
Electronic State ◽  
Intensity Distribution ◽  
Ground State ◽  
Electronic Transition ◽  
Wavelength Region ◽  
Vibronic Coupling ◽  
Banded Structure ◽  
Vibrational Levels ◽  
Type C

Rotational analyses have been carried out, with varying degrees of completeness, for nine bands of S16O2 and two bands of S18O2 in the region 3000–3300 Å. The bands are all highly perturbed type C bands, which go to b2 vibrational levels of the ππ* Ã1A2 electronic state. The [Formula: see text] electronic transition shows an anomalous vibrational intensity distribution, which indicates that the Ã1A2 state undergoes strong Born–Oppenheimer (nuclear momentum) vibronic coupling with the [Formula: see text] electronic state. All the obvious banded structure in this wavelength region can be assigned to the [Formula: see text] transition. Although no analyses of bands belonging to the [Formula: see text] transition have been carried out (since the [Formula: see text] state is so massively perturbed by the ground state), reasons are presented for placing its (0,0) band between 3100 and 3160 Å.

scholarly journals Patterns and paschen-back analogue in the stark-effect for neon

1929 ◽  
Vol 123 (791) ◽  
pp. 80-103 ◽  
Keyword(s):  
Quantum Number ◽  
Stark Effect ◽  
Selection Rule ◽  
Theoretical Calculations ◽  
Zeeman Effect ◽  
Final States ◽  
Outer Electron ◽  
Initial State ◽  
Final State ◽  
Left Handed

While the Stark-effect has not been studied so extensively as the Zeeman-effect, either in the experiments or in their interpretations, many of the more prominent features have been observed and have received adequate explanation on the quantum theory. Among these may be mentioned the patterns characteristic of the different series in the singlet system of parhelium. The variety of observed patterns in the Stark-effect, as contrasted with the normal Zeeman-effect found for all series of this system, arises from a differential action of the external electric field on the initial and final states, and a breaking down of the usual selection rule for the azimuthal quantum number. Some simplification is brought about, however, by the fact that only the absolute value of the quantum number m has any meaning in the interpretation of these photographs, since the action of the field is the same for right or left-handed motion of the outer electron in its orbit. This results in asymmetrical patterns for all the lines. The number of components observed in the patterns of individual lines of parhelium is in accord with the theoretical view that the vector j (here equal to l ) is resolved along the direction of the applied field to give the integral m values ranging from - j to + j , and that the usual selection rule holds for m . The displacements and intensities are in excellent agreement with the theoretical calculations based on the perturbation theory of quantum mechanics. The spacing of the sub-levels identified by ± m in the initial state is decidedly irregular in the Stark-effect as compared with the normal Zeeman-effect, where the displacements are proportional to m . The Zeeman order of the levels is usually reversed, in fact, and the spacing is uneven. Displacements in the final state are theoretically very small, and have not been observed with certainty. In the Stark-effect for orthohelium (triplet system) the same group of patterns was observed. An explanation of these observations, which is slightly less satisfactory than that obtained with parhelium, has been made by similar methods, neglecting the electron spin. Thus the m values were again given ranges determined in each case by the l of the outer electron, and not by the j for the whole atom. Most of the plates failed to reveal any of the fine structure of the normal orthohelium spectrum.

The ionization of H and He + by electron impact

1965 ◽  
Vol 287 (1408) ◽  
pp. 105-122 ◽  
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Born Approximation ◽  
Threshold Energy ◽  
Initial State ◽  
Ionization Cross ◽  
Final State ◽  
Comparison With Experiment ◽  
Oppenheimer Approximation ◽  
Ionization Cross Sections

The ionization cross-sections of H and He + from the ground state and excited 2 s state for incident electron energies from threshold to about four times threshold energy are calculated. The strong coupling between the hydrogenic 1 s , 2 s and 2 p states is explicitly allowed for in the initial state, and the final state is taken to be an appropriate combination of Coulomb wave functions of the two outgoing electrons. Comparison with experiment for ground-state ionization shows that the method is an improvement over the Born approximation particularly for He + . New results are presented for the Born approximation in He + ionization and for the Born-Oppenheimer approximation for both H and He + ionization. Finally, conclusions are drawn from the results concerning the validity of methods for calculating ionization cross-sections from excited states.

scholarly journals Quantum analysis of the rotational structure of the first positive bands of nitrogen (N 2 )

1932 ◽  
Vol 136 (829) ◽  
pp. 114-144 ◽  
Keyword(s):  
Electronic Configuration ◽  
Selective Excitation ◽  
Nitrogen Molecule ◽  
Rotational Structure ◽  
Positive System ◽  
Initial State ◽  
Final State ◽  
Active Nitrogen ◽  
Quantum Analysis ◽  
Vibrational Levels

The greenish-yellow afterglow of active nitrogen was first described, by Lewis. Two decades have passed since Fowler and Strutt showed that this afterglow was due to a selective excitation of a few green, yellow and red bands belonging to the first positive system of the nitrogen molecule (N 2 ). Recent work on active nitrogen indicates that the selective excitation is due to metastable nitrogen atoms giving up their energy to metastable nitrogen molecules in state A, the final state of the first positive bands, thus leading to the selective excitation of certain specific vibrational levels in state B, the initial state of the first positive bands. The molecule then returns to state A, at the same time emitting the bands which constitute the afterglow. From the rotational analysis of the second positive nitrogen bands by Lindau, and Hulthèn and Johansson, it is known that state B corresponds to a 3 II state, the second positive bands having their final state in common with the initial state of the first positive bands. No definite information has been found concerning the electronic configuration of the nitrogen molecule which gives rise to state A. This can be obtained by making a detailed analysis of the rotational structure of the first positive nitrogen bands.

The carbon monoxide flame bands

1963 ◽  
Vol 275 (1362) ◽  
pp. 431-446 ◽  
Keyword(s):  
Carbon Monoxide ◽  
Excited State ◽  
High Resolution ◽  
Energy Level ◽  
Vibrational Level ◽  
Ground State ◽  
Fermi Resonance ◽  
Absorption System ◽  
Weak Absorption ◽  
Vibrational Levels

The carbon monoxide flame bands have been photographed under high resolution from an afterglow source. Bands in the wavelength range 3100 to 3800 Å show a pattern which has been reproduced by calculations of the energies of high vibrational levels of the ground state of CO 2 . The structure of this energy level pattern is strongly affected by extensive Fermi resonance in the 1 Σ + g state. The spectrum is emitted by excited CO 2 molecules which radiate to the ground state from the lowest vibrational level and from the v ´ 2 = 1 level of a B 2 state. This excited state lies approximately 46 000 cm -1 above the lowest level of the ground state, an d has an OCO angle of 122 + 2° and a CO bond length of 1*246 ± 0*008 Å. Combination of these results with the work of other authors shows that the excited state is a 1 B 2 state, and that the carbon monoxide flame bands are associated with the weak absorption system of CO 2 at 1475 Å.

The absorption spectrum of NH2 between 6250 and 9500 Å

1976 ◽  
Vol 54 (17) ◽  
pp. 1804-1814 ◽  
Author(s):  
J. W. C. Johns ◽  
D. A. Ramsay ◽  
S. C. Ross
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Ground State ◽  
Absorption System ◽  
Molecular Constants ◽  
Bending Vibration ◽  
Long Wavelength ◽  
Vibrational Levels

The earlier analysis by Dressier and Ramsay of the [Formula: see text] absorption system of NH2 has been considerably extended at the long wavelength end of the spectrum. All the low-lying vibronic levels of the excited state have been identified up to ν2′ = 8. These levels are 010(K = 0), 020(K = 1), 030(K = 0,2), 040(K = 1,3), 050(K = 0,2,4), 060(K = 1,3,5), 070(K = 0,2,4,6), and 080(K = 1,3,5,7). Large perturbations (~ 200 cm−1) have been observed between some of these levels and high vibrational levels of the ground state. Accurate molecular constants have been obtained for the ground state and for the first level involving the bending vibration (ν2″ = 1).

Rotational Analysis of Bands of the Transition of PH2

1972 ◽  
Vol 50 (19) ◽  
pp. 2265-2276 ◽  
Author(s):  
J. M. Berthou ◽  
B. Pascat ◽  
H. Guenebaut ◽  
D. A. Ramsay
Keyword(s):  
Excited State ◽  
Ground State ◽  
Electronic Transition ◽  
Rotational Analysis ◽  
Empirical Formulas ◽  
Molecular Constants ◽  
Vibrational Levels

Rotational analyses have been carried out for the 0ν′20–000 bands of the [Formula: see text] electronic transition of PH2 with ν′2 = 1–8. Approximately 1000 lines have been assigned. The earlier analysis of the 000–000 band has been extended and improved molecular constants obtained. The Hamiltonian used for this band does not fit the excited state levels with [Formula: see text]. Term values are therefore given for all observed levels. Empirical formulas are presented which give approximate fits to the higher levels. Numerous rotational perturbations are found in the excited state. Perturbations up to 0.6 cm−1 are also found in the 000 level of the excited state. These latter perturbations can only be caused by the higher vibrational levels of the ground state.

scholarly journals Solvent-Dependent Resonance Raman Excitation Profiles of 9,9'-Bianthryl

1999 ◽  
Vol 19 (1-4) ◽  
pp. 51-56
Author(s):  
Gregory D. Scholes ◽  
Thierry Fournier ◽  
David Phillips ◽  
Anthony W. Parker
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ground State ◽  
Electronic Excitation ◽  
Electronic Absorption Spectra ◽  
Excited Electronic State ◽  
Resonance Raman ◽  
Initial State ◽  
Solvent Environment ◽  
Raman Excitation Profiles

Dynamics subsequent to the electronic excitation of 9,9′-bianthryl produce a polar emissive excited state for which the symmetry of the bichromophore is broken by a dynamic solvent stabilisation of one of the two, otherwise degenerate, charge transfer configurations which contribute to the excited electronic state. The initial state created upon excitation is examined here by analysis of ground state resonance Raman excitation profiles (REPs) and electronic absorption spectra in solvents of various polarities. The results suggest that the REPs are signalling electronic differences between the initially excited state in the various solvents. We suggest that this is related to the bianthryl excited state being responsive to the disordered solvent environment.

THE 1600 Å BAND SYSTEM OF AMMONIA

1961 ◽  
Vol 39 (4) ◽  
pp. 479-501 ◽  
Author(s):  
A. E. Douglas ◽  
J. M. Hollas
Keyword(s):  
Excited State ◽  
High Resolution ◽  
Electronic State ◽  
Band System ◽  
Excited Electronic State ◽  
Degenerate State ◽  
Coriolis Interaction ◽  
Plane Vibration ◽  
Vibrational Levels ◽  
Out Of Plane

The progression of ammonia bands which extends from 1689 to 1400 Å has been photographed in absorption at high resolution. Six bands have been analyzed and found to be of the perpendicular type. The analysis shows that the molecule is planar in the excited state and that vibrational levels observed in the progression are those of the out-of-plane vibration. The excited electronic state is of the E′′ type. In addition to the normal Coriolis interaction of the degenerate levels, a second effect has been observed which behaves like the Coriolis interaction recently described as 'giant l-type doubling' by Garing, Nielsen, and Rao. No clear evidence has been found for any distortion of the degenerate state from D3h symmetry.

Molecular Modelling of Ground- and Excited-States Vibrations in Organic Conducting Devices: Hexakis(n-hexyloxy)triphenylene (HAT6) as Case Study

2010 ◽  
Vol 63 (3) ◽  
pp. 388 ◽  
Author(s):  
M. Zbiri ◽  
M. R. Johnson ◽  
L. Haverkate ◽  
F. M. Mulder ◽  
G. J. Kearley
Keyword(s):  
Excited State ◽  
Electronic State ◽  
Ground State ◽  
Density Functional ◽  
Excited Electronic State ◽  
Molecular Vibrations ◽  
Functional Theory ◽  
Model Calculations ◽  
Insight Into

In order to gain insight into fundamental aspects of organic photocell materials, we have calculated ground and excited electronic-state structures and molecular vibrations for an isolated HAT6 molecule (hexakis(n-hexyloxy)triphenylene). Excited-state calculations are carried out using time-dependent density functional theory and frequencies are evaluated analytically using coupled perturbed Kohn–Sham equations. These model calculations have been validated against new infrared and ultraviolet data on HAT6 in solution. The main allowed valence excitation, having the largest oscillator strength, is chosen for the structural and vibrational investigations. Comparison with the ground-state vibrational dynamics reveals surprisingly large spectral differences. In addition, the alkoxy tails, which are usually considered to play only a structural role, are clearly involved in the molecular vibrations and the structural distortion of the excited electronic state compared with the ground state. The tails may play a more important role in charge separation, transport and excited-state relaxation than was previously thought. In this case, chemical modification of the tails would allow vibrational and related properties of organic photocell materials to be tailored.

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