FORBIDDEN TRANSITIONS IN DIATOMIC MOLECULES: IV. THE a′3Σ+ ← XlΣ+ AND e3Σ− ← X1Σ+ ABSORPTION BANDS OF CARBON MONOXIDE

1955 ◽  
Vol 33 (12) ◽  
pp. 757-772 ◽  
Author(s):  
G. Herzberg ◽  
T. J. Hugo
Keyword(s):  
Carbon Monoxide ◽  
Diatomic Molecules ◽  
Electronic Transitions ◽  
Absorption Bands ◽  
Unusual Structure ◽  
Precise Data ◽  
Forbidden Transitions ◽  
Perturbation Data ◽  
Vibrational Constants ◽  
Heteronuclear Molecules

Two examples of forbidden electronic transitions in heteronuclear molecules, 3Σ+ – 1Σ+ and 3Σ− – 1Σ+, are studied in the spectrum of the CO molecule. The bands have been obtained in absorption in the region 1750 to 1230 Å with absorbing paths up to 400 cm-atm., using the fourth and fifth orders of a 3 meter vacuum spectrograph. In most of the 3Σ+ – 1Σ+ bands all four predicted branches are observed. For the 3Σ− – 1Σ+ bands, a somewhat unusual structure is predicted: two branches of O and S form and three branches of Q form. In the best-resolved bands, four branches are observed which closely fit the predicted branches, two of the Q branches being very nearly coincident and unresolved in the present spectra. The rotational and vibrational constants of the upper states, a′3Σ+ and e3Σ− of the two band systems have been determined. Some of these data had previously been obtained from perturbations in other band systems of CO. On the whole, the perturbation data agree satisfactorily with the more precise data obtained directly in the present study.

FORBIDDEN TRANSITIONS IN DIATOMIC MOLECULES: I. THE QUADRUPOLE ROTATION–VIBRATION SPECTRUM OF H2

1950 ◽  
Vol 28a (2) ◽  
pp. 144-152 ◽  
Author(s):  
G. Herzberg
Keyword(s):  
Ground State ◽  
Vibration Spectrum ◽  
Diatomic Molecules ◽  
Electronic Ground State ◽  
Forbidden Transitions ◽  
Vibrational Constants ◽  
Electronic Ground

Four lines of the 2–0 band and four lines of the 3–0 band of the quadrupole rotation–vibration spectrum of H2 have been observed and measured using effective absorbing paths of 10 to 50 km. atm. From this spectrum improved values of the rotational and vibrational constants of H2 in its electronic ground state have been obtained.

THE FORBIDDEN I1Σ−–X1Σ+ ABSORPTION BANDS OF CARBON MONOXIDE

1966 ◽  
Vol 44 (12) ◽  
pp. 3039-3045 ◽  
Author(s):  
G. Herzberg ◽  
J. D. Simmons ◽  
A. M. Bass ◽  
S. G. Tilford
Keyword(s):  
Carbon Monoxide ◽  
Selection Rule ◽  
Vacuum Ultraviolet ◽  
Ultraviolet Region ◽  
Absorption Bands ◽  
Coriolis Interaction ◽  
Dipole Radiation ◽  
Vacuum Ultraviolet Region ◽  
Vibrational Constants ◽  
Π State

The forbidden I1Σ−–X1Σ+ transition of CO has been observed in absorption at high resolution in the vacuum ultraviolet region. As expected for a 1Σ−–1Σ+ transition, the bands consist of single Q branches, in which the lines of lowest J are either missing or very weak. Although the selection rule prohibiting Σ−–Σ+ transitions is rigorous for dipole radiation at zero rotation, the I1Σ−–X1Σ+ transition can occur for higher rotational levels because of Coriolis interaction with the A1Π state, which lies very close to the I1Σ− state.Eight bands of the I–X system have been analyzed and from them the rotational and vibrational constants of the I1Σ− state have been determined. Previous information on this state was based entirely on the study of perturbations in the A1Π state. The corresponding perturbations in the I1Σ− state have now been observed. In addition, small "vibrational" perturbations in the ν = 4 and 5 levels (probably caused by interactions with the a3Π state) are found.

FORBIDDEN TRANSITIONS IN DIATOMIC MOLECULES: III. NEW AND ABSORPTION BANDS OF THE OXYGEN MOLECULE

1953 ◽  
Vol 31 (4) ◽  
pp. 657-669 ◽  
Author(s):  
G. Herzberg
Keyword(s):  
Diatomic Molecules ◽  
Oxygen Molecule ◽  
Electron Configuration ◽  
Absorption Bands ◽  
Rotational Constants ◽  
Forbidden Transitions ◽  
New Formula

Two new forbidden transitions of the O2 molecule have been found. They give rise to very faint absorption bands overlapping the much stronger forbidden [Formula: see text] bands previously described. The upper states are identified as [Formula: see text] and 3Δu respectively, both of which arise from the same electron configuration as the known states [Formula: see text] and [Formula: see text]. For the [Formula: see text] state the following vibrational and rotational constants have been determined: Te = 36678.91, ωe = 650.49, ωexe = 17.036, ωeye = −0.1056, ωeze = −0.00744, Be = 0.8261, αe = 0.0205, γe = −0.000830 cm.−1, γe = 1.597 × 10−5 cm. The constants are based on the assumption of a certain vibrational numbering which may have to be revised (increased). For the 3Δu state the data are quite fragmentary and only two rotational constants, B5 = 0.8177, B6 = 0.7915, and one vibrational quantum, [Formula: see text], have been determined. The bands of the [Formula: see text] system are very close to those of the [Formula: see text] system and represent in all probability the analogue in free O2 of the diffuse triplet bands of Wulf, Finkelnburg, and Steiner ascribed to O4. The positions of the new [Formula: see text] and 3Δu states agree closely with those predicted by Moffitt. Almost half of the unidentified features of the spectrum of the nightglow agree within 5 Å with the predicted positions of emission bands of the [Formula: see text] system.

scholarly journals The spectrum of thallium chloride

1938 ◽  
Vol 166 (925) ◽  
pp. 238-249 ◽  
Keyword(s):  
The Other ◽  
Electronic Transitions ◽  
Sufficient Information ◽  
Thallium Chloride ◽  
Band Spectra ◽  
Vibrational Constants

The results of a study of the spectrum of thallium fluoride (TIF) which have already been published (Howell 1937) contained so many points of unusual interest that it was considered desirable to extend the investigation to the other halides of thallium. In particular it was hoped to acquire sufficient information concerning the electronic transitions in TICI to enable a comparison to be made of the electronic levels of this molecule with those of TIF. Furthermore, certain of the vibrational constants of TICI, as listed in such reference works as Jevons' "Report on Band Spectra" (1932) and Sponer’s "Molekülspektren" (1936) seemed so abnormal as to justify a re-examination of this spectrum.

Structural, electronic and spectroscopic features of the dihydride Pd4(dppm)4(H)22+ cluster catalyst

2001 ◽  
Vol 79 (5-6) ◽  
pp. 552-559 ◽  
Author(s):  
Daniel Meilleur ◽  
Pierre D Harvey
Keyword(s):  
Low Frequency ◽  
Inert Atmosphere ◽  
Electronic Transitions ◽  
Absorption Bands ◽  
Palladium Hydride ◽  
H Nmr ◽  
Significant Difference ◽  
Simple Selection ◽  
Centrosymmetric Structure ◽  
Ft Raman

1H NMR, vibrational, and UV–vis spectroscopic measurements for Pd2(dppm)2Cl2 (dppm = Ph2PCH2PPh2), [Pd4(dppm)4(X)2](BF4)2 (X = Cl, H), and [Pd4(dmpm)4(H)2](Br)2 (dmpm = Me2PCH2PMe2) were performed to address the structure of the recently identified title cluster. Its dmpm analogue was prepared from the reaction between Pd2(dmpm)2Br2 and NaBH4 in methanol under inert atmosphere, and exhibits the expected nonet (rel. int. 1:8:28:56:70:56:28:8:1) at –5.21 ppm (in (CD3)2CO), contrasting with that of Pd4(dppm)4(H)22+ (δ + 5.15 ppm, (CD3)2CO). This significant difference is explained by the presence of the PdH residues in the deshielding region of the dppm-phenyl groups. The vibrational spectra in the low-frequency region are consistent with a centrosymmetric structure, and a scattering at 144 cm–1 in the FT-Raman spectra is observed; a peak that is assigned to ν(Pd2) on the basis of a comparison with the well established M2-bonded Pd2(dppm)2Cl2 data ((Pd2) = 149 cm–1). On the basis of the qualitative temperature behavior of the band maxima and width, the two lowest energy absorption bands in the UV–vis spectra are assigned to d σ [Formula: see text] d σ * type transition. EHMO computations predict four well-isolated frontier MO levels, defined as d σ *(Pd2)/d σ *(PdH) (LUMO + 1), d σ *(Pd2) (LUMO), d σ *(Pd2)/d σ *(PdH) (HOMO), and d σ (Pd2) (HOMO –1), and simple selection rules (u « g) indicate that only two low-energy electronic transitions are orbitally allowed, consistent with the UV–vis findings. Computer modelings show the presence of large cavities above and under the Pd4 plane, described by inner-cavity nonbonded H···H distances of ~5–8 Å.Key words: cluster, palladium, hydride, structure, spectroscopy.

scholarly journals High Resolution Spectroscopy With Molecular Beams and Tunable Lasers

1998 ◽  
Vol 18 (1-2) ◽  
pp. 1-11 ◽  
Author(s):  
R. Vetter ◽  
P. Luc ◽  
C. Amiot
Keyword(s):  
Electronic Structure ◽  
High Resolution ◽  
Diatomic Molecules ◽  
Reaction Dynamics ◽  
Molecular Beams ◽  
Tunable Lasers ◽  
High Resolution Spectroscopy ◽  
Absorption Bands ◽  
Quantum Numbers ◽  
Laser Techniques

High resolution Doppler-free laser techniques are used in beam experiments to improve the spectroscopic description of complex diatomic molecules. The case of TiO is considered here for its implication in reaction dynamics studies and its interest in Astrophysics. Two absorption bands in the visible have been analyzed: B3Π−X3 Δ(1−0) and c1Φ−a1 Δ(0−0). Owing to accurate wavenumber measurements, it has been possible to extend the analysis to high rotational quantum numbers and to carry out detailed spectroscopic calculations. They show that a careful revisiting of the TiO electronic structure is necessary.

The electronic spectra of osmium and ruthenium tetroxides

1967 ◽  
Vol 20 (11) ◽  
pp. 2315 ◽  
Author(s):  
EJ Wells ◽  
AD Jordan ◽  
DS Alderdice ◽  
IG Ross
Keyword(s):  
Electronic Spectra ◽  
Detailed Structure ◽  
Absorption Bands ◽  
Forbidden Transitions

The spectrum of OsO4 has been measured in the vapour and in solution. Detailed structure reported in the main absorption bands by Langseth and Qviller was not reproduced. The irregularity of the main intervals between peaks, and their sensitivity to temperature, bespeak a perturbed spectrum which is too diffuse to analyse convincingly. Three fragmentary systems of quite different appearance were observed in all samples and could well be weak forbidden transitions. The spectrum of RuO, vapour is no better resolved. Reproducible features of both spectra are tabulated.

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