The A2Πi–X2Πi band system of ClO: Reinvestigation of the absorption spectrum

1976 ◽  
Vol 54 (10) ◽  
pp. 1034-1042 ◽  
Author(s):  
J. A. Coxon ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Ground State ◽  
Flash Photolysis ◽  
Band System ◽  
Resolving Power ◽  
Kcal Mole ◽  
Molecular Constants ◽  
Long Range Interactions ◽  
State Dissociation ◽  
First Time

The A2Πi–X2Πi band system of 35ClO has been reinvestigated in absorption in the flash photolysis of ClO2 and Cl2/O2 mixtures, using higher resolving power than in earlier work. The rotational assignments for the ν′–0 progression have been revised and extended and new molecular constants have been obtained. In addition, four new bands with ν″ = 1 and 2 have been observed for the first time. The value for the ground state vibrational interval is found to be [Formula: see text]. Widths are given for levels with 2 ≤ ν′ ≤ 25 and show that all these levels are predissociated. With the help of the theory of long-range interactions, an improved value for the ground state dissociation energy is obtained, viz. D0″ = 22 184 ± 3 cm−1 (≡ 63.427 ± 0.008 kcal/mole ≡ 2.7504 ± 0.0004 eV).

THE ABSORPTION SPECTRUM AND DISSOCIATION ENERGY OF SH

1961 ◽  
Vol 39 (1) ◽  
pp. 210-217 ◽  
Author(s):  
J. W. C. Johns ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Dissociation Energy ◽  
Ground State ◽  
Kcal Mole ◽  
Energy Formula ◽  
Vibrational Constants ◽  
State Dissociation ◽  
First Time

The (2,0) bands of the A2Σ+−X2Π system of SH and SD have been photographed for the first time. More accurate values for the vibrational constants of the A2Σ+ state have been obtained. The dissociation energy of SH in the excited state is [Formula: see text] from which it is possible to deduce that the ground state dissociation energy [Formula: see text] (SH) is 28,480 ± 1000 cm−1 (81.4 ± 2.9 kcal/mole, 3.53 ± 0.12 ev).

THE ABSORPTION SPECTRUM OF BO2

1961 ◽  
Vol 39 (12) ◽  
pp. 1738-1768 ◽  
Author(s):  
J. W. C. Johns
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Detailed Analysis ◽  
Ground State ◽  
Flash Photolysis ◽  
Electronic Transitions ◽  
Molecular Constants ◽  
Boron Trichloride ◽  
Symmetric Molecule ◽  
First Excited State

The boron flame bands have been observed in absorption during the flash photolysis of mixtures of boron trichloride and oxygen. Detailed analysis of the spectrum has shown that the bands arise from two electronic transitions in the linear symmetric molecule BO2, [Formula: see text] and A2Πu−X2Πg. The main molecular constants, in cm−1 except for r0, are summarized below:[Formula: see text]Both 2Π states show the Renner effect. In the ground state the Renner parameter, εω2, was found to be −92.2, whereas in the first excited state it is much smaller, −13.1 cm−1.

The spectrum and structure of the free BH 2 radical

1967 ◽  
Vol 298 (1453) ◽  
pp. 142-159 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Ground State ◽  
Electronic Transition ◽  
Flash Photolysis ◽  
Molecular Constants ◽  
Isotope Shifts ◽  
Geometrical Data

A new absorption spectrum has been found in the flash photolysis of H 3 BCO which, from its structure and the observed isotope shifts can be unambiguously assigned to the free BH 2 radical. The spectrum represents a transition similar to those previously observed in NH 2 and CH 2 . The molecule is linear in the excited state but bent (with an angle of 131°) in the ground state. Molecular constants and geometrical data are evaluated. The electronic transition is 2 B 1 ( II u ) – 2 A 1 and fits well with expectation from the Walsh diagram for X H 2 molecules.

The electronic spectra of phenyl radicals

1965 ◽  
Vol 287 (1411) ◽  
pp. 457-470 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Spectra ◽  
Flash Photolysis ◽  
Visible Region ◽  
Electronic Configuration ◽  
Vibrational Structure ◽  
Fundamental Frequencies

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm -1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm -1 which correspond to the e 2 g and a 1 g frequencies of the B 2 u state of benzene. The ground state of phenyl has a π 6 n electronic configuration and the observed transition is interpreted as 2 A 1 → 2 B 1 resulting from a π → n excitation.

THE ABSORPTION SPECTRUM OF CF2

1967 ◽  
Vol 45 (7) ◽  
pp. 2355-2374 ◽  
Author(s):  
C. Weldon Mathews
Keyword(s):  
Absorption Spectrum ◽  
Electronic State ◽  
Ground State ◽  
Band System ◽  
Electronic States ◽  
Vibrational Structure ◽  
Rotational Structure ◽  
Transition Moment ◽  
High Dispersion ◽  
Parallel Type

The absorption spectrum of CF2 in the 2 500 Å region has been photographed at high dispersion, and the rotational structure of a number of bands has been analyzed. The analysis of the well-resolved subbands establishes that these are perpendicular- rather than parallel-type bands, as previously assigned. Further analysis shows that the upper and lower electronic states are of 1B1 and 1A1symmetries respectively, corresponding to a transition moment that is perpendicular to the plane of the molecule. In the upper electronic state, r0(CF) = 1.32 Å and [Formula: see text], while in the ground state, r0(CF) = 1.300 Å and [Formula: see text]. An investigation of the vibrational structure of the band system has shown that the vibrational numbering in ν2′ must be increased by one unit from earlier assignments, thus placing the 000–000 band near 2 687 Å (37 220 cm−1). A search between 1 300 and 8 500 Å showed two new band systems near 1 350 and 1 500 Å which have been assigned tentatively to the CF2 molecule.

The 1650-1350 Å absorption spectrum of nitrogen dioxide

1962 ◽  
Vol 267 (1330) ◽  
pp. 395-407 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Nitrogen Dioxide ◽  
Ionization Potential ◽  
Ground State ◽  
Band System ◽  
Anharmonic Constant ◽  
Rydberg Transitions ◽  
First Ionization Potential

An analysis of the 1650-1350 Å band system of nitrogen dioxide has been carried out. A pattern of band spacings and intensities is found that is complex but regular. It is shown that this pattern is qualitatively, and to a large extent quantitatively, just what would be expected for a transition in which the shape of the molecule changes from bent to linear. The transition is a parallel one and the upper state has 2 Σ + u symmetry. The symmetrical stretching frequency is increased from its ground-state value to ca. 1420 cm -1 in the upper state. The upper-state bending frequency is ca. 600 cm -1 . The N — O length is decreased from its groundstate value, probably to 1·1(3) Å. The upper state resembles closely the ground state of NO + 2 . The transition is to be classed as one of the Rydberg transitions leading to the first ionization potential of NO 2 ; and the orbital to which the odd electron is transferred in the transition is (pσ) in type. The anharmonic constant g 22 for the linear upper state is found to be 2·(3) cm -1 . Other Rydberg transitions may well be present in the region, but have not been definitely identified.

The analysis of a 2 A 1 - 2 B 1 electronic band system of the AsH 2 and AsD 2 radicals

1968 ◽  
Vol 305 (1481) ◽  
pp. 271-290 ◽  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Flash Photolysis ◽  
Band System ◽  
Valence Angle ◽  
Electronic Transitions ◽  
Doublet State ◽  
Electronic Band ◽  
Asymmetric Rotor ◽  
Asymmetric Top

Two new band systems have been observed in absorption following flash photolysis of AsH 3 and AsD 3 , and are assigned to 2 A 1 - 2 B 1 electronic transitions of AsH 2 and AsD 2 . The origins of both systems are at 19905 cm -1 . The bands have the complex rotational structure associated with an asymmetric rotor. Rotational analyses have been carried out for three bands of the AsH 2 spectrum, leading to the following molecular parameters: ground state, r" 0 = 1.518 Å valence angle = 90° 44'; excited state, r' 0 = 1.48 Å, valence angle = 123° 0'. The parameters associated with rotation about the a inertial axis increase rapidly with increase in v' 2 . The spectrum shows doublet splittings of up to 41 cm -1 , and the excited state furnishes the first example of a doublet state of an asymmetric top molecule which shows substantial departures from Hund’s case ( b ).

A re-investigation of the A 2 ∑+-X 2 ∏ i band system of NCO

1975 ◽  
Vol 343 (1632) ◽  
pp. 17-44 ◽  
Keyword(s):  
Free Radical ◽  
Ground State ◽  
Band System ◽  
Resolving Power ◽  
Absorption System ◽  
Bending Vibration ◽  
Electron Resonance

The A 2 Σ+ -X 2 II 1 (a) absorption system of the NCO free radical has been re-investigated with higher resolving power than in the earlier work of Dixon (i960). Particular emphasis has been directed to the rotational analyses of bands involving the three vibronic levels, μ 2 Σ (+) , 2 Δ i -(a) and k 2 Σ (-) , associated with the first level of the bending vibration in the ground state. A misassignment in the earlier work has been corrected and a new value for the Renner parameter determined, namely ε = -0.144 ± 0.001. This revised value removes the discrepancy noted in the earlier electron resonance results.

The A2Πi–X2Πi absorption spectrum of BrO

1981 ◽  
Vol 59 (12) ◽  
pp. 1908-1916 ◽  
Author(s):  
M. Barnett ◽  
E. A. Cohen ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Ground State ◽  
Flash Photolysis ◽  
Absorption Bands ◽  
Long Wavelength ◽  
Numbering Scheme ◽  
Ozonized Oxygen ◽  
Good Agreement

Absorption spectra of isotopically enriched 81Br16O and of normal BrO have been obtained by the flash photolysis of mixtures of bromine and ozonized oxygen. Rotational analyses are given for the 7–0, 12–0, 18–0, 19–0, 20–0, 21–0, 7–1, and 20–1 A2Π3/2–X2Π3/2 sub-bands of 81Br16O. The value for [Formula: see text] is found to be 722.1 ± 1.1 cm−1 in good agreement with the value calculated from microwave constants. Several additional bands have been found at the long wavelength end of the spectrum, necessitating a revision of the vibrational numbering scheme for both the emission and absorption bands. "Hot" bands up to ν″ = 6 have been observed in the absorption spectrum for the 2Π3/2 component of the ground state but no bands have yet been identified from the 2Π1/2 component.

BAND SPECTRUM AND STRUCTURE OF THE CH+ MOLECULE; IDENTIFICATION OF THREE INTERSTELLAR LINES

1942 ◽  
Vol 20a (6) ◽  
pp. 71-82 ◽  
Author(s):  
A. E. Douglas ◽  
G. Herzberg
Keyword(s):  
Ground State ◽  
Band System ◽  
Lower State ◽  
Band Spectrum ◽  
Interstellar Space ◽  
Molecular Constants ◽  
Vibrational Levels ◽  
State Formula ◽  
Heat Of Dissociation ◽  
Π State

In a discharge through helium, to which a small trace of benzene vapour is added, a new band system of the type 1Π – 1Σ is found which is shown to be due to the CH+ molecule. The R(0) lines of the 0–0, 1–0, and 2–0 bands of the new system agree exactly with the hitherto unidentified interstellar lines 4232.58, 3957.72, 3745.33 Å, thus proving that CH+ is present in interstellar space. At the same time this observation of the band system in absorption shows that the lower state 1Σ is the ground state of the CH+ molecule. The new bands are closely analogous to the 1II – 1Σ+ BH bands. The analysis of the bands leads to the following vibrational and rotational constants of CH+ in its ground state: [Formula: see text], Be″ = 14.1767, αe″ = 0.4898 cm.−1. The internuclear distance is re″ = 1.1310∙10−8 cm. (for further molecular constants see Table V). From the vibrational levels of the upper 1Π state the heat of dissociation of CH+ can be obtained within fairly narrow limits: D0(CH+) = 3.61 ± 0.22 e.v. From this value the ionization potential of CH is derived to be I(CH) = 11.13 ± 0.22 e.v. The bearing of this value on recent work on ionization and dissociation of polyatomic molecules by electron impacts is briefly discussed.

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