scholarly journals Gas-phase ultraviolet absorption spectrum of nitric acid vapor

1973 ◽  
Vol 77 (1) ◽  
pp. 62-63 ◽  
Author(s):  
Harold Johnston ◽  
Richard Graham
Keyword(s):  
Absorption Spectrum ◽  
Nitric Acid ◽  
Gas Phase ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
Acid Vapor

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

scholarly journals The Near-ultraviolet Absorption Spectrum of Diimide Vapor

1974 ◽  
Vol 52 (6) ◽  
pp. 1006-1012 ◽  
Author(s):  
R. A. Back ◽  
C. Willis ◽  
D. A. Ramsay
Keyword(s):  
Absorption Spectrum ◽  
Bond Length ◽  
Gas Phase ◽  
Absorption Spectra ◽  
Ground State ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
Near Ultraviolet ◽  
Bending Mode ◽  
Franck Condon

Absorption spectra of N2H2 and N2D2 in the gas phase have been obtained in the region 3000–4300 Å, consisting of about 30 diffuse bands for each compound. Long progressions in the spectra are attributed to excitation of the H—N=N bending mode, v2′, in the upper state, with much shorter progressions arising from the N=N stretching mode, v3′; values of v2′ = 1215 and 910 cm−1 and v3′ = 1550 and 1440 cm−1 were estimated for N2H2 and N2D2 respectively.The spectra are attributed to the 1Bg ← 1Ag(π* ← n+) transition of trans diimide, probably made allowed by vibronic interaction. From Franck–Condon calculations the H—N=N angle in the upper state was estimated to be 132 ± 2°, an increase of 25° from the ground-state value; the increase in the N=N bond length was estimated to be about 0.05 Å.

The ultraviolet absorption spectrum of oxalic acid vapor

1984 ◽  
Vol 62 (8) ◽  
pp. 1414-1428 ◽  
Author(s):  
R. A. Back
Keyword(s):  
Absorption Spectrum ◽  
Fine Structure ◽  
Oxalic Acid ◽  
Vibrational Analysis ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
Absorption System ◽  
Acid Vapor ◽  
Medium Resolution ◽  
Partial Analysis

The ultraviolet absorption spectrum of oxalic acid vapor has been studied for the first time. Low-resolution spectra show a moderately weak (εmax = 25 M−1 cm−1 at 277 nm) banded absorption system beginning at about 310 nm and extending to 250 nm where a stronger absorption begins. Medium-resolution spectra show a complex vibrational fine-structure at wavelengths above about 287 nm, with many sharp line-like R-branch heads, each corresponding to a different vibrational transition. A vibrational analysis was completed for 12C2O4H2, 12C2O4D2, and 13C2O4H2, and electronic origins were estimated to be at 31903.2, 31970.2, and 31949.4 cm−1, respectively (about 313 nm). Strong features were assigned to progressions in [Formula: see text] the C=O and C—O stretching vibrations, with prominent sequences in ν10, the C—C torsional vibration, running to the blue, implying that [Formula: see text].This absorption system has been assigned to the first excited singlet state, designated Ã, corresponding to a π* ← n+, 1Au ← 1Ag transition of planar trans-oxalic acid. High-resolution spectra of several bands show rotational fine-structure, and a partial analysis was carried out on the [Formula: see text], and [Formula: see text] bands of 12C2O4H2, based on apparently-simple diverging P-branches.

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