The Band System of the CCO Molecule

1971 ◽  
Vol 49 (22) ◽  
pp. 2839-2858 ◽  
Author(s):  
C. Devillers ◽  
D. A. Ramsay
Keyword(s):  
Transient Absorption ◽  
Flash Photolysis ◽  
Energy Levels ◽  
Fermi Resonance ◽  
Lower State ◽  
Linear Molecule ◽  
Transient Absorption Spectrum ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Sequence Band

The transient absorption spectrum observed previously (Devillers) in the flash photolysis of carbon suboxide has been studied under high resolution in the region 5000 to 9000 Å and assigned to the CCO radical. A rotational analysis of the 000–000 band near 8580 Å shows conclusively that the electronic transition is [Formula: see text]. From molecular orbital considerations the lower state is assigned as [Formula: see text]. Short progressions involving the stretching vibrations (ν1′ = 0–3, ν3′ = 0–1) have been observed. A Fermi resonance has been found involving ν3′ and 2ν2′. Some sequence bands have been assigned; in particular the 010–010 sequence band clearly shows the Renner splittings expected for the Ã3Πi excited state. A band with a different type of rotational structure has been assigned to the forbidden component 010 3Σ(−) – 000 3Σ−. The rotational analysis of this band is in excellent agreement with the theory of Hougen for the rotational energy levels of a linear molecule in the ν2 = 1 level of a 3Π state.The following molecular constants have been obtained:[Formula: see text]

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]

ABSORPTION SPECTRUM OF THE CCN RADICAL

1965 ◽  
Vol 43 (10) ◽  
pp. 1795-1830 ◽  
Author(s):  
A. J. Merer ◽  
D.N. Travis
Keyword(s):  
Absorption Spectrum ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Energy Levels ◽  
Transient Absorption Spectrum ◽  
Molecular Constants ◽  
Angular Momenta ◽  
Show Evidence ◽  
Vibrational Energy Levels

A new transient absorption spectrum, attributed to the CCN free radical, has been discovered in the flash photolysis of diazoacetonitrile, HC(CN)N2; three electronic transitions, between 3 500 Å and 4 700 Å, have been photographed for both CC14N and CC15N. The ground state of the radical is a 2Πr electronic state, and the three excited states observed are A2Δ, B2Σ−, and C2Σ+. The 2Π and 2Δ states show evidence of Renner–Teller interaction between the vibrational and electronic angular momenta, an effect not observed previously for 2Δ states. Theoretical expressions for the vibrational energy levels of linear triatomic molecules in 2Δ electronic states have been derived, in terms of a parameter η associated with the quartic terms in the potential energy. They are compared with the observed pattern in the ν2 = 1 level of the A2Δ state. The principal molecular constants for CC14N (in cm−1) are as follows:[Formula: see text]

Transient absorption spectra of chlorine and bromine

1963 ◽  
Vol 276 (1364) ◽  
pp. 51-68 ◽  
Keyword(s):  
Absorption Spectra ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Light Output ◽  
Inert Gases ◽  
Rotational Analysis ◽  
Molecular Constants ◽  
Quantum Process ◽  
Bromine Chloride ◽  
Transient Absorption Spectra

New absorption spectra of chlorine (2500 to 2100 Å) and bromine (2900 to 2400 Å are reported. They were obtained by the flash photolysis of a mixture of halogen and inert gas. The spectral lifetimes were never > 50 μs and the intensities were approximately in phase with the light output of the photolysis lamp. Both spectra consist of a long, slowly converging v " = 0 progression of bands which degrade to the red. Whereas the bromine bands obtained on medium and large quartz spectrographs revealed no fine structure, the chlorine spectrum taken on a grating instrument was seen to possess a diffuse, rotational structure. A rotational analysis of the chlorine spectrum was made and band head wavelengths and molecular constants for both halogens are recorded. By means of an isotope effect a v ' numbering of the chlorine bands has been put forward. It is thought th at the spectra result from a two-quantum process and th a t the final transition is from 3 Π o+, u to a higher level, possibly 0 + g . A vibrational perturbation occurs in the chlorine spectrum and predissociation is postulated. The effect of filters, inert gases and oxygen on the spectra is discussed and reasons are suggested why analogous spectra for bromine chloride and iodine were not observed.

Photochemical Properties of 2-Aryl-3-imino-1-indones

1992 ◽  
Vol 47 (12) ◽  
pp. 1243-1247 ◽  
Author(s):  
I. Timtcheva ◽  
N. Getoff ◽  
P. Nikolov ◽  
R. M. Quint
Keyword(s):  
Absorption Spectrum ◽  
Steady State ◽  
Reaction Mechanisms ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Uv Light ◽  
Transient Absorption Spectrum ◽  
Light Illumination ◽  
Probable Reaction ◽  
Photochemical Properties

Steady state as well as flash photolysis experiments of 2-aryl-3-imino-1-indones (2-AIID) have been carried out with the aim to learn more about their photochemical properties. It was established that in ethanol these substances exist solely in the keto-enamine-form and are rather photostable under the influence of uv-light. Illumination in dichloroethane, acetonitrile and dioxane is leading to stable photoproducts. A typical transient absorption spectrum of 2-AIID is presented. Probable reaction mechanisms are given.

Photoinduced electron transfer in a supramolecular triad system composed of ferrocene-zinc porphyrin-pyridylnaphtha-lenediimide

2007 ◽  
Vol 11 (05) ◽  
pp. 368-374 ◽  
Author(s):  
Shunichi Fukuzumi ◽  
Yukiyasu Kashiwagi
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Zinc Ion ◽  
Transient Absorption Spectrum ◽  
Zinc Porphyrin ◽  
Long Lifetime ◽  
Porphyrin Moiety

A supramolecular ferrocene-zinc porphyrin-pyridylnaphthalenediimide triad is formed by coordinating the pyridine entity of pyridylnaphthalenediimide with the zinc ion of a ferrocene-zinc porphyrin dyad in benzonitrile. The fluorescence of the zinc porphyrin moiety is efficiently quenched by photoinduced electron transfer from the singlet excited state of the zinc porphyrin moiety to the naphthalenediimide moiety. This is followed by subsequent electron transfer from the ferrocene moiety to the zinc porphyrin radical cation to produce the final charge-separated state, ferricenium ion-zinc porphyrin-naphthalenediimide radical anion, which is successfully detected as a transient absorption spectrum in the laser flash photolysis. The decay of the charge-separated state obeys first-order kinetics irrespective of the initial concentration of the charge-separated state to afford a long lifetime (320 μs). This is the first example of a supramolecular triad that has a long lifetime as compared with the charge-separated state lifetime of the component dyad.

Absorption spectroscopy of singlet CH2 near 11 200 cm–1

2001 ◽  
Vol 79 (2-3) ◽  
pp. 347-358 ◽  
Author(s):  
K Kobayashi ◽  
T J Sears
Keyword(s):  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Energy Levels ◽  
Zero Point ◽  
Laser Flash ◽  
Infrared Region ◽  
Transient Absorption Spectroscopy

New spectra of methylene, CH2, in the near infrared region of the singlet band system have been obtained. They were detected by laser transient absorption spectroscopy following excimer laser flash photolysis of ketene, CH2CO, at 308 nm. The new data provide information on the nature and energies of rotational levels in three vibronic states that lie between approximately 11 500 and 13 000 cm–1 above the zero point level of the lower, ã1A1, state. Taken together with previous measurements, a fairly complete picture of the vibronic energy levels of CH2 in this region can be built up. There is generally good agreement with the recent computational studies on the singlet states of CH2, but some evidence for discrepancies for levels with K = 3 and higher near the minimum of the [Formula: see text]1B1 potential surface. PACS No.: 33.20Ea

An extremely long-lived charge-separated state of zinc tetraphenylporphyrin coordinated with pyridylnaphthalene-diimide

2006 ◽  
Vol 10 (12) ◽  
pp. 1371-1379 ◽  
Author(s):  
Kenji Saito ◽  
Yukiyasu Kashiwagi ◽  
Kei Ohkubo ◽  
Shunichi Fukuzumi
Keyword(s):  
Photoinduced Electron Transfer ◽  
Lower Energy ◽  
Transient Absorption ◽  
Laser Excitation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Transient Absorption Spectrum ◽  
Triplet Excited State ◽  
Donor Acceptor

The nitrogen of pyridylnaphthalenediimide ( PyNIm ) coordinates to the metal center of zinc tetraphenylporphyrin ( ZnTPP ) to form a donor-acceptor complex: ZnTPP-PyNIm . Formation of the ZnTPP-PyNIm complex was probed by UV-vis, fluorescence and NMR spectra. The fluorescence of ZnTPP is strongly quenched and the fluorescence lifetime is shortened significantly in the complex. The transient absorption spectrum of the charge-separated state ( ZnTPP •+- PyNIm •-) is successfully detected by laser flash photolysis measurements of the ZnTPP-PyNIm system in benzonitrile. The charge-separated state of the complex produced by the photoinduced electron transfer has the longest lifetime, (450 μs) at 288 K, ever reported for donor-acceptor systems linked covalently or non-covalently in solution. However, when benzonitrile is replaced by benzene, the triplet excited state (3 ZnTPP* ), rather than the charge-separated state, is formed upon laser excitation of the ZnTPP-PyNIm complex, due to the lower energy of (3 ZnTPP* ) compared to the charge-separated state in benzene.

scholarly journals Picosecond Flash Photolysis of Photochromic Spiropyrans

1984 ◽  
Vol 4 (1-6) ◽  
pp. 129-138 ◽  
Author(s):  
S. A. Krysanov ◽  
M. V. Alfimov
Keyword(s):  
Room Temperature ◽  
Internal Conversion ◽  
Transient Absorption ◽  
Flash Photolysis ◽  
Decay Channel ◽  
Transient Absorption Spectrum ◽  
Colored Form ◽  
Pyran Ring ◽  
Decay Times ◽  
Buildup Time

The transient species involved in photocoloration and photobleaching of indoline 6-nitrosubstituted spiropyran solutions at room temperature were studied by picosecond flash photolysis. Transient absorption spectrum of spiropyran colorless form consists of two bands peaked at 440 and 585 nm and is assigned to the photoinduced intermediate non-planar cis configuration with the breaked C—O bond of the pyran ring. This transient is found to have the buildup time shorter than 10 ps and initial decay times of about 10 ns in benzene and 5 ns in ethanol. The colored form exhibits the transient absorption peaked at 460 nm with the lifetime of about 200 ps in ethanol which is assigned to Sn ← S1 absorption of colored form. The predominant decay channel of the colored form S1 state is shown to be internal conversion S1 ⇝ S0 with the quantum yield of about 0.70 ± 0.15.

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.

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