Absorption Spectrum Of Bromine Research Articles

Quenched by ice: Transient grating measurements of vibronic dynamics in bromine-doped ice

In both water and in ice, the absorption spectra of bromine are dramatically broadened and blueshifted, and all fluorescence is quenched. Time resolved, electronically resonant transient grating measurements are carried out to characterize the vibronic dynamics of the trapped molecule in its electronic B(3Pi0u) state in ice. Independent of the initial excitation energy, after the first half-period of motion, a vibrational packet is observed to oscillate near the bottom of the potential, near nu=1. The oscillations undergo a chirped decay to a terminal frequency of 169 cm(-1) on a time scale of taunu=1240 fs, to form the stationary nu=0 level. The electronic population in the B state decays in taue=1500 fs. Adiabatic following to the cage-compression coordinate is a plausible origin of the chirp. Analysis of the absorption spectrum is provided to recognize that solvent coordinates are directly excited in the process. The observed blueshift of the absorption is modeled by considering the Br2-OH2 complex. Two-dimensional simulations, that explicitly include the solvent coordinate, reproduce both the time data and the absorption spectrum. The observed sharp vibrational recursions can be explained by overdamped motion along the solvent coordinate, and wave packet focusing by fast dissipation during the first half-period of motion of the molecular coordinate.

Bromine−AOT Charge-Transfer Complexes and Hydrogen-Bond Donor Ability of Water in AOT−isooctane−H2O Reverse Micelles and Water-in-Oil Microemulsions

Changes, induced by aerosol-OT (sodium bis(2-ethylhexyl) sulfosuccinate, AOT), in the absorption spectrum of bromine, are shown to markedly depend on the nature and the hydration of the AOT-aggregates. A charge-transfer complex (CTC) between bromine and monomeric AOT (λmax = 270 nm, ε315 = 1.4 × 103 cm-1 M-1, and K = 4 × 103 M-1) is observed in isooctane, in agreement with a very strong electron donor ability of AOT, attributed to its sulfonate headgroup. In “dry” reverse micelles ([AOT] > cmc), the constant for the CTC formation K = 1.3 M-1 is markedly smaller. In aqueous reverse micelles, the observed ε decrease (ε315 = 700 cm-1 M-1 and K = 1.1 M-1 for W = [H2O]/[AOT] = 9) is consistent with a competition between water and bromine in the stabilization of the AOT-head groups. Finally, in water-in-oil (w/o) microemulsions (W > 12), the complex disappears. The bromine−tribromide ion equilibrium is also investigated in AOT-w/o microemulsions in the presence of bromide ions. The marked dependence of the equilibrium constant for Br3- formation on the microemulsion composition (W= 12, K = 178 M-1; W ≥ 20, K = 60 M-1; bulk water, K = 16 M-1) is attributed to a change in the transfer free energy of bromide ion from bulk water to the aqueous pseudophase of the microdroplets (δΔGtr (Br-) = −2.6 and −1.3 kcal mol-1 for W = 12 and 20, respectively). The results are discussed in terms of changes in the hydrogen-bond donor ability and polarity of water in AOT−w/o microemulsions.

Absorption spectrum of atomic bromine (Br I) in the vacuum ultraviolet region

The absorption spectrum of bromine was photographed in the region 900-1700 AA on a three-metre normal-incidence spectrograph. The absorption cell consisted of a flash pyrolysis system and the background continuum source was a Garston flash lamp. The Rydberg series converging on 4p4 3P2, 3P1, 3P0 and 1D2 have been greatly extended. One hundred and fourteen additional lines have been classified, more than doubling the number of the classified lines in this region.

The vacuum ultraviolet spectrum of the bromine molecule

The absorption spectrum of bromine has been photographed in the first and higher orders of a 10.7-m. concave vacuum grating spectrograph in the region 1700–1170 Å.A number of band systems have been obtained in the region 1510–1170 Å, most of which correspond to Rydberg transitions. In addition, an extensive band system with closely-spaced bands degraded to longer wavelengths has been recorded in the region 1700–1500 Å. Among the Rydberg systems, five series have been found to converge to 85 165 ± 80 cm−1 which represents the ionization potential of the molecule leading to the 2Π3/2g state of the molecular ion. They arise due to transitions from the ground state to [σg2πu4πg32Π3/2g]npσu, [σg2πu4πg32Π3/2g]npπu, [σg2πu4πg32Π3/2g]nfσu, [σg2πu4πg32Π3/2g]nfπu, and [σg2πu4πg32Π3/2g]nfδu configurations where n takes the running values 5, 6, 7, … etc. The first few members of four similar series corresponding to the transitions to the states involving the [σg2πu4πg32Π1/2g] core have been identified and the ionization limit of these series is estimated to be at 88 306 ± 80 cm−1. Two of the remaining band systems have been found to be very likely due to transitions to the Rydberg states with the configurations [σg2πu3πg42Π3/2u]5sσg and [σg2πu3πg42Π1/2u]5sσg, respectively. Three of the observed systems which do not involve Rydberg states appear to have for their upper levels the 1Πu(1u), 3Π(1u), and 3Π(0u+) states arising from the configuration σgπu3πg4σu2.

Absorption spectrum of bromine from 6200 to 5100 Å

The absorption spectrum of the 3Π0+u–1Σ+g system of bromine between 6200 and 5100 A has been photographed at high resolution using each of the separated isotopic species 79Br2 and 81Br2. A rotational analysis of ten bands of each isotopic species has been carried out. The accepted vibrational numbering was confirmed. The constants obtained (cm–1) for each species are:- [graphic omitted]. Revised constants for the most abundant isotopic species 79 81Br2 have been calculated. The last four bands immediately preceding the onset of the continuum have also been analyzed for each species. A limiting curve of dissociation has been plotted in each case leading to an average value for D0(79 81Br2) of 15,893.1 ± 1.0 cm–1.

Wavelength Measurement in Echelle Spectra

A method for the accurate measurement of wavelength in echellegrams is described. It differs from previous methods in being applicable to a spectrograph with a continuously variable projection-length, such as a variable wavelength Littrow lens spectrograph. Any line in an echelle spectrum is characterized by the ratio l/L, where L is the distance between two arbitrary marks at opposite ends of the prism spectrograph slit, and l is the distance of the echelle line from one of them. By fitting a quadratic curve to the known spectrum of neon, the “unknown” wavelengths of a mercury-cadmium spectrum are derived with an accuracy of better than 1 in 106. It is shown that a linear curve is adequate for certain complex spectra such as the absorption spectrum of bromine. Allowance can be made for line shifts due to thermal, mechanical, or pressure causes.

The Primary Photochemical Process in Bromine

THE absorption spectrum of bromine exhibits a continuum which commences at about 5107 A., and it is known that the absorption of light of wavelength less than this value causes the dissociation of bromine into an atom in its normal 2 P 3/2 state and one in the excited 2 P ½ state. Photochemical studies have shown that bromine molecules are also dissociated when irradiated with light of wavelengths greater than 5107 A. Thus the quantum yield of the hydrogen–bromine reaction1 is approximately the same at 5460 A. as for light of wavelength in the continuum, that is, 5107 A. Further, it has been demonstrated that the quantum yield2,3 for the photobromination of ethylene is independent of wave-length between the limits 4800 and 6800 A.

Note on the interpretation of the visible absorption spectrum of bromine

The accurate construction of the lower parts of the potential-energy curves for the excited states involved in the transitions responsible for the visible absorption spectrum of bromine has enabled a choice to be made between two possible alternative interpretations.

The Absorption Spectrum of Bromine at High Temperatures

The Absorption Spectrum of Bromine at High Temperatures

VI. On the absorption-spectra of bromine and of iodine monochloride

The element bromine and the compound iodine monochloride possess nearly the same molecular weight. The colours of their vapours appear almost identical, and a rapid glance at the complicated absorption-spectra afforded by the two gases fails to detect any difference between them. It becomes, therefore, a matter of importance to ascertain whether the molecules of the two bodies, when gaseous, vibrate identically or similarly. We have accordingly undertaken a series of exact measurements of the absorption-spectra of these two gases, the results of which we have now the honour to communicate to the Royal Society. The two spectra were compared simultaneously by means of one of Kirchhoff’s model spectroscopes, 4 flint-glass prisms of 60° and 45° and a magnifying-power of 40 being employed. The position of the lines and of the well-defined edges of the bands in both spectra were read off by reflexion upon a fixed arbitrary scale; the positions of 27 air-lines lying between the extremes of the absorption-spectra were then determined upon the same scale, both the scale and prisms remaining untouched during the different series of observations. In order to determine the wave-lengths of each of the absorption-bands in the spectra of bromine and iodine monochloride, the wave-length of each of the 27 air-lines was ascertained by reference to the measurements of Thalén; in three cases, marked H, in the accompanying Table the numbers given by Huggins have been used.

Societies and Academies

LONDONRoyal Society, May 4.—“On the Absorption-Spectra of Bromine and Iodine Monochloride,” by H. E, Roscoe, F.R.S., and T. E Thorpe.