THE ABSORPTION SPECTRUM OF THE Si2 MOLECULE

1963 ◽  
Vol 41 (1) ◽  
pp. 152-160 ◽  
Author(s):  
R. D. Verma ◽  
P. A. Warsop
Keyword(s):  
Absorption Spectrum ◽  
Dissociation Energy ◽  
Ground State ◽  
Flash Photolysis ◽  
Lower State ◽  
The Third ◽  
Photolysis Apparatus ◽  
Vibrational Constants

Three band systems of Si2 have been found in absorption with a flash photolysis apparatus. Two of the band systems at 3200 and 2100 Å are new, whereas the third is an extension of the 3Σ–3Σ system observed by Douglas in emission. All three systems have the same lower state and arise from [Formula: see text] transitions. It is very probable that the [Formula: see text] state is the ground state of the Si0 molecule. Rotational and vibrational constants of all four 3Σ states have been determined. The dissociation energy of Si2 is estimated to be 3.0 ± 0.2 ev.

Absorption spectrum of the Mg2 molecule

1970 ◽  
Vol 48 (7) ◽  
pp. 901-914 ◽  
Author(s):  
W. J. Balfour ◽  
A. E. Douglas
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
High Resolution ◽  
Potential Energy ◽  
Dissociation Energy ◽  
Ground State ◽  
Potential Energy Curve ◽  
Energy Curve ◽  
Vibrational Constants

The absorption spectrum of the Mg2 molecule, which occurs in a furnace containing Mg vapor, has been photographed with a high resolution spectrograph. The rotational structures of the bands have been analyzed and the rotational and vibrational constants of the two states determined. The bands are found to arise from a 1Σ–1Σ transition between a very lightly bonded ground state and a more stable excited state. The R.K.R. potential energy curve of the ground state, which has a dissociation energy of 399 cm−1, has been determined. The more important constants of the ground state are ωe = 51.12 cm−1, ωexe = 1.64 cm−1, re = 3.890 Å and those of the upper state are ωe = 190.61 cm−1, ωexe = 1.14 cm−1, re = 3.082 Å.

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 SH AND SD IN THE VACUUM ULTRAVIOLET

1966 ◽  
Vol 44 (10) ◽  
pp. 2447-2459 ◽  
Author(s):  
B. A. Morrow
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Vacuum Ultraviolet ◽  
Flash Photolysis ◽  
Electronic States ◽  
Rydberg Series ◽  
A Value ◽  
Vibrational Constants

The absorption spectrum of SH in the vacuum ultraviolet has been obtained by the flash photolysis of hydrogen sulfide. Transitions from the 2Π ground state to seven excited states have been observed and four of these fit reasonably well into a Rydberg series. From an extrapolation to the convergence limit of this series, a value of 10.40 ± 0.03 eV for the ionization potential of SH has been derived. Values for the rotational constants of these new electronic states have been determined; corresponding data for SD have also been obtained. The (1–0) transition of the system near 1 670 Å (B2Σ–X2Π) was observed, and, with the aid of isotope relations, vibrational constants of the B state have been derived. An estimate of the dissociation energy of SH in this excited state is D0′ = 24 190 ± 1 000 cm−1.

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 SO and the flash photolysis of sulphur dioxide and sulphur trioxide

1959 ◽  
Vol 249 (1259) ◽  
pp. 498-512 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Dissociation Energy ◽  
Sulphur Dioxide ◽  
Flash Photolysis ◽  
Ultra Violet ◽  
Vibrationally Excited ◽  
A Value ◽  
Continuous Absorption ◽  
Sulphur Trioxide ◽  
Normal Spectrum

The flash photolysis of sulphur dioxide under adiabatic conditions results in the complete temporary disappearance of its spectrum , which then slowly regains its original intensity over a period of several milliseconds. Simultaneously with the disappearance of the sulphur dioxide spectrum a continuous absorption appears in the far ultra-violet and fades slowly as the sulphur dioxide reappears. It is shown that the effect of the flash is thermal rather than photochemical, and the possibility of the existence of an isomer of sulphur dioxide at high temperatures is discussed; the disappearance of the normal spectrum on flashing is explained in this way. Several previously unrecorded bands of SO observed in the photolysis indicate that the vibrational numbering of its spectrum should be revised by the addition of 2 to the present values of v' . This leads to a value of the dissociation energy of 123.5 kcal. In formation about the levels v' = 4, 5 and 6 has also been obtained. The isothermal flash photolysis of sulphur trioxide results in the appearance of vibrationally excited SO, and the primary photochemical step in this reaction is discussed.

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.

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 7500 to 4500 Å absorption system of the free HCO radical

1955 ◽  
Vol 233 (1192) ◽  
pp. 34-54 ◽  
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Flash Photolysis ◽  
Lower State ◽  
Absorption System ◽  
Molecular Plane ◽  
Bending Mode ◽  
Vibrational Levels ◽  
Other Substances ◽  
Low Dispersion

A fairly extensive absorption spectrum o f the free HCO radical produced by flash photolysis of acetaldehyde and other substances has been investigated with long absorbing paths and under high resolution. The corresponding DCO spectrum has also been studied. The absorption spectrum consists of simple bands with P, Q and R branches. It is shown that the molecule is linear in the upper state, but bent in the lower state with an angle of about 120° and a CO bond length of approximately 1.20 Å. Rotational constants of HCO and DCO in both upper and lower states have been derived. Various arguments based on the high-resolution measurements lead to the conclusion that the main progression of bands corresponds to transitions to the vibrational levels of the upper state with even v' 2 (the vibrational quantum number of the bending mode). This conclusion is confirmed by the observation under low dispersion of some of the intermediate bands with odd v’ 2 which are diffuse and therefore not easily recognizable under high resolution. Apparently all levels of the upper state with l≠0 are predissociated. The type of the electronic transition is shown to be 2 Σ+ ← 2 A”, that is, the transition moment is perpendicular to the molecular plane. The lower state cannot arise from normal CO and H.

ABSORPTION SPECTRA OF C3 AND C3H2 FROM THE FLASH PHOTOLYSIS OF DIAZOPROPYNE

1967 ◽  
Vol 45 (12) ◽  
pp. 4103-4111 ◽  
Author(s):  
A. J. Merer
Keyword(s):  
Absorption Spectrum ◽  
Free Radical ◽  
Ground State ◽  
Time Delays ◽  
Flash Photolysis ◽  
State Level ◽  
Vibrational Structure ◽  
Absorption Bands ◽  
Text Component ◽  
Ground State Level

The flash photolysis of diazopropyne (HC2∙CHN2) provides a particularly strong absorption spectrum of the free C3 radical. About 40 μs after the photolysis flash, the appearance of the [Formula: see text] (4 050 Å) system of C3 is similar to that obtained in the flash photolysis of diazomethane by Gausset, Herzberg, Lagerqvist, and Rosen, though much more intense. The intensity of the spectrum has permitted a study of the l-type doubling effect in the ground-state level 6ν2, of which the [Formula: see text] component has been found to lie at 458.2 cm−1. At shorter time delays [Formula: see text] the spectrum is complicated by bands arising from the levels ν1″ (1 224.5 cm−1) and 2ν1″ (2 436.0 cm−1).Below 3 700 Å the C3 spectrum is overlapped by absorption bands belonging to a new free radical, which has been identified from the intensity alternation in the rotational structure as the HCCCH radical. The vibrational structure of this system is exceptionally complex, and analysis has not been possible. The bands extend to about 3 100 Å, but are predissociated below 3 450 Å.

SPECTRUM AND STRUCTURE OF THE FREE HNCN RADICAL

1963 ◽  
Vol 41 (2) ◽  
pp. 286-298 ◽  
Author(s):  
G. Herzberg ◽  
P. A. Warsop
Keyword(s):  
Fine Structure ◽  
Ground State ◽  
Electronic Transition ◽  
Flash Photolysis ◽  
Geometrical Structure ◽  
Transition Moment ◽  
Lower State ◽  
State Formula ◽  
Exact Position

A widely spaced perpendicular band at 3440 Å observed in the flash photolysis of diazomethane is ascribed to the free HNCN radical. The study of the fine structure of this band for HNCN, DNCN, and HNC13N has yielded information about the geometrical structure of the molecule in both the upper and lower (ground) state. For the lower state[Formula: see text]The N—C—N group is very nearly linear, but the exact position of the C atom on this line could not be determined. The electronic transition is of the type 2A′–2A″, the transition moment being perpendicular to the plane of the molecule.

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