ABSORPTION SPECTRA OF HCCl AND DCCl

1966 ◽  
Vol 44 (3) ◽  
pp. 525-547 ◽  
Author(s):  
A. J. Merer ◽  
D. N. Travis
Keyword(s):  
Bond Length ◽  
Flash Photolysis ◽  
Energy Levels ◽  
Large Change ◽  
Absorption Bands ◽  
Bending Vibration ◽  
Equilibrium Angle ◽  
Vibrational Levels ◽  
Type C ◽  
Axis Switching

A long progression of absorption bands appearing in the region 5 500–8 200 Å has been observed in the flash photolysis of dibromochloromethane, HCClBr2. Observation of chlorine and deuterium isotope shifts, together with the results of the rotational analyses, have shown that the carrier of the bands is the chloromethylene radical, HCCl.The ground state of HCCl is a 1A′ state in which the molecule has an equilibrium angle of ~103°, a C—H bond length of 1.12 Å, and a C—Cl bond length of 1.69 Å. In the upper state, of character 1A″, unusual patterns of the vibrational and K-type rotational energy levels indicate that the molecule, although bent, has a low barrier to linearity and is easily "straightened" by vibration. The vibrational levels of the upper state may be fitted quite accurately, using a potential function for the bending vibration of the type suggested by Thorson and Nakagawa (1960); our calculations show that the equilibrium angle in the upper state is ~135° and that the top of the barrier lies 2 250 cm−1 above the lowest vibrational level.The large change of angle in the transition causes the appearance of subbands with ΔK = 0 and −2 in addition to those allowed by the strict type-C selection rules. The intensities of the forbidden subbands are well explained by the axis-switching mechanism suggested by Hougen and Watson (1965).

ROTATIONAL ANALYSIS OF BANDS OF THE HCF MOLECULE

1966 ◽  
Vol 44 (7) ◽  
pp. 1541-1550 ◽  
Author(s):  
A. J. Merer ◽  
D. N. Travis
Keyword(s):  
Transient Absorption ◽  
Flash Photolysis ◽  
Bond Angle ◽  
Large Change ◽  
Transient Absorption Spectrum ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Ordinary Type ◽  
Type C ◽  
Axis Switching

A new transient absorption spectrum, belonging to the HCF free radical, has been discovered in the flash photolysis of dibromofluoromethane, HCFBr2. The spectrum consists of a single progression of complex bands in the region 4 300–6 000 Å. Rotational analysis of the less severely perturbed bands shows them to be type-C bands of a molecule that is nonlinear in both upper and lower states of the transition, with bond angles of ~ 127° and ~ 102° respectively. Axis-switching effects, due to the large change of bond angle in the transition, cause the appearance of prominent gQ, qQ, and °Q branches, in addition to those obeying the ordinary type-C selection rules.The principal molecular constants of HCF (in cm−1) are:[Formula: see text]

The electronic absorption spectra of NH 2 and ND 2

1959 ◽  
Vol 251 (1002) ◽  
pp. 553-602 ◽  
Keyword(s):  
Excited State ◽  
Bond Length ◽  
Absorption Spectra ◽  
Flash Photolysis ◽  
Electronic Absorption Spectra ◽  
Interaction Constant ◽  
Bending Vibration ◽  
Vibronic Structure ◽  
Linear Configuration ◽  
Centrifugal Distortion Constants

The absorption spectra of <super>14</super>NH 2 , <super>15</super>NH 2 and <super>14</super>ND 2 have been photographed in the region 3900 to 8300 A with a 21 ft. concave grating spectrograph. The radicals are produced by the flash photolysis of <super>14</super>NH 3 , <super>15</super>NH 3 and <super>14</super>ND 3 respectively. A detailed study of the <super>14</super>NH 2 - <super>15</super>NH 2 isotope shifts suggests that the molecule has a linear configuration in the excited state and that the spectrum consists of a long progression of the bending vibration in this state. These conclusions have been confirmed by detailed rotational and vibrational analyses of the 14NH2 and 14ND2 spectra. The spectra consist of type C bands for which the transition moment is perpendicular to the plane of the molecule. For NH2, sixteen bands of the progression (0, v'%, 0) <- (0, 0, 0) have been identified with v'% — 3, 4, ..., 18. In addition four bands of a subsidiary progression (1, v'2, 0) <- (0, 0, 0) have been found; these bands derive most of their intensity from a Fermi-type resonance between (0, v'2) 0) and (1, v2 —4, 0) levels in the excited state. The interaction constant W nl is 72 + 3 cm <super>-1</super>. For ND 2 , fourteen bands of the principal progression (v2 — 5 to 18) and one band of the subsidiary progression have been identified. The upper state vibration frequencies w?' and (i)' are 3325 cm <super>-1</super> and 622 cm <super>-1</super> for NH 2 and 2520 cm <super>-1</super> and 422 cm <super>-1</super> for ND 2 respectively. The bending frequencies are unusually low ; moreover, the anharmonicities of the bending vibration are unusually large and negative (x22—11.4 cm <super>-1</super> for NH 2 and 8.1 cm <super>-1</super> for ND 2 ). The origin of the system lies in the region o f 10000 cm <super>-1</super>. Ground-state rotational term values have been derived from observed com bination differences; values for the rotational constants Aooo, B'ooo and Cooo and for the centrifugal distortion constants D"A, D"b and D"0 have been determined. The bond lengths and bond angles for NH 2 and ND 2 agree and are 1.024 + 0.005 A and 103° 20' + 30' respectively. Small spin splittings have been observed. In the excited state an unusual type of vibronic structure has been found. Successive levels of the bending vibration consist alternately of 27, d , T, ... and ... vibronic sub-levels with large vibronic splittings. The origins of the vibronic sub-bands may be represented by the formula yf = Vq—GK2, where G is ~ 27 cm -1 for NH 2 and ~ 19 cm <super>-1</super> for ND 2 . The rotational levels show both spin and A-type doubling. No simple formula has been found to fit the energies o f the II, A, 0 and -T rotational levels; the 27 levels fit the formula F(N) = 1) — D N2(N + 1)2, though with a negative value for D . By extrapolating the B values for the 27 levels to = 0 we obtain B'00o = 8.7 8 cm <super>-1</super> for NH 2 and 4.4 1 cm<super>-1</super> for ND 2 . These values are consistent with a linear configuration with a bond length of 0.97 5 A. The significance of this short bond length is discussed. An explanation of the complex vibronic structure is given. The two combining states are both derived from an electronic II state which is split by electronic-vibrational coupling for the reasons advanced by Renner. A detailed correlation diagram is given. A quantitative treatment of this effect by Pople & Longuet-Higgins gives good agreement with the experimental data.

The absorption spectrum of the free NCO radical

1960 ◽  
Vol 252 (1007) ◽  
pp. 165-192 ◽  
Keyword(s):  
Flash Photolysis ◽  
Ultra Violet ◽  
Fermi Resonance ◽  
Spin Splitting ◽  
Lower State ◽  
State Transitions ◽  
Absorption Bands ◽  
Bending Vibration ◽  
Rotational Constants ◽  
Coupling Case

Two systems of absorption bands have been observed in the visible and ultra-violet regions of the spectrum during the flash photolysis of several organic cyanates, and have been photographed under high resolution with long absorbing paths. Extensive vibrational and rotational analyses have been carried out for the bands of one system and show that the spectrum is due to an electronic transition A ( 2 Z + ) <-- X ( 2 II < i ) of the free NCO radical, which is linear in both states. All three vibrational frequencies and the first-order anharmonic constants have been obtained for the upper state, A ( 2 { + ), and give a close fit to the term values of 21 observed vibrational levels. A Fermi resonance has been observed between v ' 1 and 2v' 2 . In addition, the rotational constants B' and D' and their variations with all three fundamental vibrations have been obtained for this state. Transitions have been observed from four excited levels of the bending vibration in the lower state, X ( 2 II i ), and the rotational constants have been determined for some of these levels. Interaction between the electronic and vibrational motions (Renner effect) complicates the vibrational structure of this state. The state belongs to Hund’s coupling case ( a ), and the spin-orbit coupling gives a splitting A" = —95.6 cm<super>-1</super>. In a 2 { + vibronic level of this state (arising from l = 1 and A = 1) the spin sp litting is proportional to N +1/2, but the spin-splitting constant y is unusually large, and amounts to 30 % of the B value. The electronic states of NCO are correlated with those of its dissociation products. This shows that the bond dissociation energy of the CO bond is slightly greater than that of the CN bond in the three known states.

scholarly journals Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christian Wiebeler ◽  
Joachim Vollbrecht ◽  
Adam Neuba ◽  
Heinz-Siegfried Kitzerow ◽  
Stefan Schumacher
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Energy Levels ◽  
Spectroscopic Properties ◽  
Absorption Bands ◽  
Functional Theory ◽  
Vertical Excitation ◽  
Hartree Fock ◽  
Tauc Plot ◽  
Electrochemical Approach

AbstractA detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.

Vibration-rotation bands and rotational constants of dideuteroacetylene

1955 ◽  
Vol 232 (1190) ◽  
pp. 291-309 ◽  
Keyword(s):  
Resolving Power ◽  
Vibrational States ◽  
Absorption Bands ◽  
Rotational Constants ◽  
Vibrational Assignments ◽  
Vibrational Anharmonicity ◽  
A Value ◽  
Vibrational Levels ◽  
Vibration Rotation ◽  
Very High

Nine vibrational absorption bands of dideutero-acetylene have been examined with very high resolving power. The rotational constants have been determined for the vibrational levels concerned, and the coefficients α i have been determined with more convincing accuracy than previously. In some of the bands the Q branches have been resolved, so that the l -doubling coefficients q i could be derived, and details could be established about the doublet components in some II levels. The results emphasize the need of high resolution if the vibrational assignments are to be unambiguous, and if reliable values of the rotational constants are to be derived. A value of B e has been obtained, and the vibrational anharmonicity coefficients have been considered briefly. Estimates of the centrifugal stretching constants D i in different vibrational states have been made, and one anomalous case has been found.

scholarly journals Anab initiobased full-dimensional potential energy surface for OH + O2⇄ HO3and low-lying vibrational levels of HO3

2019 ◽  
Vol 21 (25) ◽  
pp. 13766-13775 ◽  
Author(s):  
Xixi Hu ◽  
Junxiang Zuo ◽  
Changjian Xie ◽  
Richard Dawes ◽  
Hua Guo ◽  
...  
Keyword(s):  
Potential Energy ◽  
Potential Energy Surface ◽  
Quantum Dynamics ◽  
Energy Surface ◽  
Vibrational Energy ◽  
Energy Levels ◽  
Vibrational Levels ◽  
Vibrational Energy Levels

A full-dimensional potential energy surface for HO3, including the HO + O2dissociation asymptote, is developed and rigorous quantum dynamics calculations based on this PES have been carried out to compute the vibrational energy levels of HO3.

Chemical Treatment Influence on the Glass Substrate to the Growth of V2O5/PANI Thin Film

2009 ◽  
Vol 1230 ◽  
Author(s):  
Elidia M. Guerra ◽  
Mirela C. Santos ◽  
Rodrigo Fernando Bianchi
Keyword(s):  
Thin Film ◽  
Chemical Treatment ◽  
Energy Levels ◽  
Direct Reaction ◽  
Absorption Bands ◽  
Lbl Films ◽  
Ammonia Detection ◽  
Cetyl Pyridinium ◽  
Uv Ozone

AbstractGrowth of the vanadium pentoxide xerogel in the presence of the polyaniline thin film (V2O5/PANI) in different chemical treatment on substrate are presented. The in situ characterization studies revealed the presence of a lamellar structure for the V2O5/PANI hybrid material. The intercalation reaction was evidenced on the basis of the increase in the d-spacing as well as the displacement of the absorption bands toward lower energy levels. The growth of V2O5/PANI thin film, from direct reaction, on glasses substrate using pre-treated with cationic surfactant cetyl pyridinium chloride (CPC) and cetyl trimethylammonium bromide (CTAB) presented layers with a surface homogeneous. The UV/ozone and RCA treatment showed that the film had low adhesion on substrate compared with CPC and CTAB treatment. Furthermore, these results suggests that the CTAB and CPC treatment can be used, further, for V2O5/PANI LbL films using V2O5 gel as first layer as well as a promising candidate for applications as sensor for ammonia detection in poultry shed.

scholarly journals Calculations of CO2 Energy Levels: The Ã1B2 State

1971 ◽  
Vol 40 ◽  
pp. 43-43
Author(s):  
W. S. Benedict
Keyword(s):  
Carbon Monoxide ◽  
Energy Levels ◽  
Vibrational Levels ◽  
Upper Level ◽  
Vibration Rotation

The Ã1B2 state of CO2, identified by Dixon (1963) as the upper level of the ‘carbon monoxide flame bands’, must be of importance in the upper atmospheres of Venus and Mars. New calculations of the high vibrational levels of the ground state, which lead to improved fits of the observed vibration-rotation bands, confirm Dixon's analysis, except that the numbering must be lowered by two, and fix the energy of the v = 0, K = 0 level of 1B2 at 45210 ± 10 cm−1 = 5.605 eV.

The visible absorption spectrum of 1,2-cyclobutanedione in the gas phase

1986 ◽  
Vol 64 (11) ◽  
pp. 2152-2161 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Energy Levels ◽  
Vibrational Structure ◽  
Visible Absorption Spectrum ◽  
Excited Singlet ◽  
Bending Vibration ◽  
Visible Absorption ◽  
Out Of Plane

The visible absorption spectrum of 1,2-cyclobutanedione has been measured in the gas phase at wavelengths between 4000 and 5100 Å. The absorption is attributed to the allowed π* ← n+, 1B1 ← 1A1 transition corresponding to the first excited singlet state. The spectrum shows a complex well-resolved vibrational structure which has been analysed, with some 125 bands measured and assigned. The bands at the longer wavelengths show sharp rotational fine structure, not yet analysed. The strongest band in the spectrum at 4933 Å has been assigned as the 0–0 band, while a band almost as strong at 4820 Å is attributed to excitation of one quantum of [Formula: see text], the a2 out-of-plane carbonyl bending vibration, and it is suggested that this band owes its intensity to vibronic coupling. A number of symmetric vibrations are also excited in the spectrum, but with no long progressions. Sequence bands running to the blue with an interval of about 72 cm−1 are prominent throughout the spectrum, and are assigned to v13, the a2 ring-twisting vibration. Other hot bands were also observed involving v13 which permitted estimation of energy levels for this vibration both in the ground state and the excited state. The infrared spectrum was also measured and analysed in the gas phase between 600 and 4000 cm−1, and 14 bands were assigned to fundamental vibrations; some of these assignments, at the lower frequencies, are uncertain.

Sign in / Sign up

Export Citation Format

Share Document