A 2Π-2Π ELECTRONIC BAND SYSTEM OF THE FREE NCO RADICAL

1960 ◽  
Vol 38 (1) ◽  
pp. 10-16 ◽  
Author(s):  
R. N. Dixon
Keyword(s):  
Dissociation Energy ◽  
Band System ◽  
Rotational Structure ◽  
Absorption Bands ◽  
Electronic Band ◽  
Stretching Vibration

A series of red-degraded absorption bands has been observed between 2650 Å and 3200 Å and is attributed to a 2Π-2Π transition of the NCO radical. The bands probably represent a progression of the upper-state stretching vibration [Formula: see text]. The rotational structure of one band has been analyzed. Diffuseness in some of the bands indicates predissociation of the upper state, and is discussed in terms of the dissociation energy of NCO.

THE ELECTRONIC EMISSION SPECTRUM AND MOLECULAR CONSTANTS OF IODINE MONOFLUORIDE

1966 ◽  
Vol 44 (2) ◽  
pp. 337-352 ◽  
Author(s):  
R. A. Durie
Keyword(s):  
High Resolution ◽  
Emission Spectrum ◽  
Dissociation Energy ◽  
Band System ◽  
Vibrational Analysis ◽  
Rotational Structure ◽  
Molecular Constants ◽  
Present Evidence ◽  
Halogen Compounds ◽  
Concave Grating

Observation by the author (Durie 1951) of a well-developed band system in the emission from an iodine–fluorine flame provided the first evidence for the existence of iodine monofluoride (IF), the last of the six possible diatomic inter-halogen compounds to be detected. The spectrum, which lies in the region 4 300 to 7 600 Å, has since been photographed under high resolution using a 21-ft concave grating spectrograph. The rotational structure of the bands is shown to be consistent with an A3Π0+ → X1Σ transition in the IF molecule. A rotational and vibrational analysis of the bands has been carried out and the molecular constants evaluated for IF. The results are as follows:[Formula: see text]The present evidence relating to the value of the dissociation energy of IF is discussed.

FORBIDDEN TRANSITIONS IN DIATOMIC MOLECULES: II. THE ABSORPTION BANDS OF THE OXYGEN MOLECULE

1952 ◽  
Vol 30 (3) ◽  
pp. 185-210 ◽  
Author(s):  
G. Herzberg
Keyword(s):  
Dissociation Energy ◽  
Band System ◽  
Opposite Sign ◽  
Dissociation Limit ◽  
Spin Orbit Coupling ◽  
Absorption Bands ◽  
Near Ultraviolet ◽  
Triplet Splitting ◽  
Forbidden Transition ◽  
Low Dispersion

The forbidden [Formula: see text] absorption bands of O2 in the near ultraviolet have been obtained under high resolution with absorbing paths up to 800 m. A detailed fine structure analysis has been carried out. It confirms the identification of the band system as a [Formula: see text] transition. Precise values of the rotational constants Bν and Dν as well as of the vibrational quanta [Formula: see text] in the upper state have been derived. Each of the "lines" of the Q branches observed under low dispersion is resolved into six components whose spacing yields the triplet splitting in the upper state. This splitting is more than twice as large as in the [Formula: see text] ground state and is of opposite sign. The splitting constants λ and γ have been determined and their variation with the vibrational quantum number observed. In addition to the Q-form branches weak O- and S-form branches have been found in agreement with the prediction of Present which is based on the assumption that spin–orbit coupling is the main cause for the occurrence of this forbidden transition. However, the relative intensities of the different branches deviate strongly from Present's prediction. The dissociation limit obtained from the convergence limit of the bands (without extrapolation) is at 41219 ± 40 cm.−1 This value is higher by about 220 cm.−1 than the value of the dissociation energy of O2 derived from the Schumann–Runge bands. It is possible that the limit of the Schumann–Runge bands, which is based on a short extrapolation, and therefore the value of the dissociation energy of O2 has to be slightly revised. The electron configurations and dissociation products of the various electronic states of O2 are briefly discussed.

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.

Infrared Absorption Spectra of Vinyl Esters of Carboxylic Acids

1970 ◽  
Vol 24 (5) ◽  
pp. 495-498 ◽  
Author(s):  
George E. McManis
Keyword(s):  
Vinyl Ester ◽  
Ester Group ◽  
Vinyl Esters ◽  
Deformation Bands ◽  
Absorption Bands ◽  
Esters Of Carboxylic Acids ◽  
Sharp Band ◽  
Out Of Plane ◽  
Stretching Vibration ◽  
Infrared Absorption Spectra

The ir spectra of compounds containing the vinyl ester group exhibit absorption bands that allow them to be readily distinguished from other monosubstituted ethylenic compounds and from other esters. The vinyl C=C stretching vibration is a strong sharp band at 1640 cm−1, which is quite useful in analytical procedures. The C–H stretching vibrations of the vinyl ester group are observed as two weaker bands at 3117 and 3040 cm−1 flanking a larger sharp band at 3091 cm−1. In-plane C–H deformation bands are noted at 1413, 1291, and 1092 cm−1, while out-of-plane deformations are at 947, 868, and 603 cm−1. The stretching vibration of the ester carbonyl is a strong sharp band at 1754 cm−1. The C–O stretching region is dominated by a very strong band at 1142 cm−1.

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 ).

Studies on metal hydroxy compounds. II. Infrared spectra of zinc derivatives ϵ-Zn(OH)2, β-ZnOHCl, ZnOHF, Zn5(OH)8Cl2, and Zn5(OH)8Cl2·H2O

1967 ◽  
Vol 45 (6) ◽  
pp. 585-588 ◽  
Author(s):  
O. K. Srivastava ◽  
E. A. Secco
Keyword(s):  
Infrared Spectra ◽  
Group Factor ◽  
Absorption Bands ◽  
Site Group ◽  
Planar Molecule ◽  
Stretching Vibration ◽  
Hydroxy Compounds ◽  
A Site ◽  
First Time ◽  
Unambiguous Assignment

Infrared spectra of ϵ-Zn(OH)2, β-ZnOHCl, ZnOHF, Zn5(OH)8Cl2, and Zn5(OH)8Cl2·H2O and their deuterated analogues in the range 2.5–16 μ are reported for the first time. The effects of substituting a halogen for an OH group in Zn(OH)2 are (i) sharper OH stretching absorption bands, (ii) splitting of bands involving OH to give distinct doublets in ZnOHF and Zn5(OH)8Cl2, indicating strong intermolecular coupling, and (iii) shift of the OH stretching vibration to a higher frequency. Strong absorption bands are observed in the region of 695–780 cm−1 for all compounds and also near 1 020 ± 30 cm−1 in all cases except ZnOHCl. All the observed bands are displaced to lower frequencies by the deuterated analogues, with vH/vD ratios in the range 1.30–1.36. A cursory interpretation of the spectra of ZnOHCl and ZnOHF is given in terms of a planar molecule of Cs symmetry, but the unambiguous assignment of the bands must await a site group or group factor analysis.

Diffuse Reflectance Infrared Spectroscopic Characterization of Silica Dehydroxylation

1990 ◽  
Vol 44 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Robert L. White ◽  
Aurobindo Nair
Keyword(s):  
Force Constant ◽  
Diffuse Reflectance ◽  
Spectroscopic Characterization ◽  
Absorption Bands ◽  
Stretching Vibration ◽  
Diffuse Reflectance Infrared ◽  
Highly Strained ◽  
Infrared Absorption Bands ◽  
Absorbance Band

Diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) is employed to study the dehydroxylation of amorphous silica. Dehydroxylation results in the appearance of infrared absorption bands at 1022, 1107, and 1240 cm−1 assigned to asymmetric stretching vibrations for three different siloxane bridge types. The 1107-cm−1 absorbance band represents a siloxane bridge that is indistinguishable from bulk species. The 1022-cm−1 absorbance band represents a siloxane bridge with a bond angle that is smaller than the bulk, with little change in the stretching vibration force constant. The 1240-cm−1 absorbance band derives from a siloxane bridge characterized by a stretching force constant significantly larger than that of bulk siloxane bridges. This band may be indicative of a highly strained or broken siloxane bridge.

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