Vibrational Levels Of Ground State Research Articles

Predissociation model for formaldehyde

The collisionless nonradiative decay of single vibronic levels of the first excited singlet state of formaldehyde (1A2) is explained in terms of coupling with vibronic levels of the ground (1A1) state. Interaction is provided by the breakdown of the Born-Oppenheimer approximation through the nuclear kinetic energy operator. A full, Franck-Condon-factor-weighted summation of states calculation is undertaken for both H2CO and D2CO. Harmonic oscillator wavefunctions derived from published spectroscopic studies are used throughout. Anharmonic mixing of the ground state vibrational levels is artificially accounted for by averaging the rate over a range of final state energies. The bound-to-bound state calculation is consistent with a two-step dissociation process, in which the excited state is less strongly coupled to the ground state than the ground state is coupled to the continuum. Direct coupling to the continuum is neglected. The results are in good agreement with experiment as regards the dependence of rate on total energy and on vibrational modes, the absolute magnitude of the rates, and the effect of isotopic substitution. Rates for levels with CH stretches excited are underestimated. The largest contributions to the rates come from coupling to ground state levels with the CO stretch and the out-of-plane bend highly excited.

The t 1 absorption and phosphorescence spectra of α-phase and γ-phase p-dichlorobenzene crystals

The T 1 absorption and emission spectra of the recently discovered α-phase of p-dichlorobenzene are presented and analyzed. New high resolution spectra of the α-phase are also reported and the analysis of the T 1 absorption spectrum is revised in light of results for the γ-phase. The frequency of the b 2g mode, involving out-of-plane chlorine motions, is found to drop by 210 cm −1 upon excitation and, as a result, it is active as a progression-forming mode in both the absorption and emission spectra. Its activity, relative :othe a g modes, is quite different in the two phases of p-dichlorobenzene and is not the same in the absorption and emission spectra. The high resolution phosphorescence spectrum of the α-phase shows detailed fine structure due to both multiple site emission and to splittings of some of the ground state vibrational levels.

Influencing parameters in time resolved picosecond spectroscopy and a new light gate method

We show that the open period of a CS 2 light gate, triggered by a picosecond optical pulse, depends on the optical pathlength through the CS 2. An alternative to the light gate is suggested for time resolved spectroscopy. The working principle is based on scattering induced in CS 2. We have found that the broadband emission from H 2O or D 2O excited by a 5300 Å picosecond pulse is also of picosecond duration, but the blue part is delayed with respect to the red. From this delay time the lifetime of the ground state vibrational levels may be measured directly.

H_2 Lyman and Werner Bands Laser Theory

The laser power densities for the Lyman and Werner bands are calculated with a complete rotational analysis. For the Lyman band, P(3) and P(1) are favored and are stronger than Werner Q(1) and P(3) transitions even though the latter are favored in excitation. The transitions from Lyman levels to the lower ground state vibrational levels, where most of the strong Werner transitions terminate, reduce the net inversion density for the Werner band.

Ground state vibrational levels of zinc uranyl acetate

Abstract The vibrational levels in the ground state of zinc uranyl acetate [Zn(UO2)2(CH3)COO)6·H2O] have been established for the first time from the investigations of Raman, infrared and fluorescence spectra of the compound and the fluorescence spectrum has been analysed on the basis of these vibrational frequencies. The Raman spectrum has been obtained with a helium-neon laser as the excitation source. The infrared absorption spectrum has been recorded by both Nujol mull and potassium bromide disc techniques. The fluorescence spectrum has been photographed with powder samples of the compound at liquid air temperature. Besides the uranyl frequencies, eleven fundamentals due to the acetate ion and three fundamentals due to the crystal lattice have been obtained in the infrared and fluorescence spectra. Good agreement has been obtained between the values of the various fundamental frequencies from the different investigations. The interpretation given for the fluorescence spectrum confirms the analysis proposed by Dieke and Duncan involving a single electronic transition from the lowest excited state of the uranyl ion to the various vibrational levels of the ground state.

Millimeter-Wave Spectrum of Hydrogen Peroxide

Some 50 rotational transitions of HOOH in the ground vibrational state have been measured in the millimeter-wave region from 60 to 300 kMc/sec. Analysis of these transitions provides a complete set of values of the rotational constants and the accurate value of 342 885.0 ± 2.0 Mc/sec for the doublet splitting of the ground-state vibrational levels by internal barrier tunneling. The rotational constants in the Hamiltonian for the semirigid-rotor model with an internal axis of rotation are (in megacycles per second): ν01,201,2 = 276 208.0 ± 2.0, ν03,403,4 = 275 912.7 ± 2.0, β01,201,2 = 25 662.1 ± 2.0, β03,403,4 = 25 673.7 ± 2.0, γ01,201,2 = 542.96 ± 0.5, γ03,403,4 = 476.64 ± 0.5. The dihedral angle of the OH bonds is found to be 120°1′ ± 15′ for the lower level and 116°7′ ± 15′ for the upper level of the ground-state doublet. Some 30 millimeter-wave rotational transitions for DOOD were also measured, but analysis of them is not yet complete.

Near-Ultraviolet Absorption Spectrum of m-Chlorobenzonitrile in Vapor Phase

The absorption spectrum of a molecule appears due to the transition between various vibrational levels of ground state to the different levels of the excited electronic states, and thus, is capable of giving detailed information regarding the vibrational frequencies of the upper electronic state and a few of the ground state. This short report presents the information about the 0,0 band and the vibrational frequencies of ground and excited electronic states of m-chlorobenzonitrile in vapor phase.

Experimental and computer studies of the kinetics and distribution of vibrational energy in both products of the reaction: O(3 P)+ CS2? SO + CS

The reaction, O(3P)+CS2→SO + CS (2), was initiated by flashing NO2+CS2 mixtures with radiation of wavelengths >3000 A. Its progress was monitored by kinetic absorption spectroscopy of the CS A1Π–X1∑+(0,0) band and these measurements yielded log10k2= 9.8(±0.2)–600(±300) cal/mole/2.303RT.At higher NO2 and CS2 concentrations, other absorption bands, from both this system and the SO B3∑––X3∑– system, were observed. By comparing the relative intensities of bands from different ground state vibrational levels, the relative rates into individual quantum states were determined and the total vibrational energy yields were estimated to be 8 % of –ΔH in CS and about 18 % in SO. A preliminary investigation of the kinematics by computer simulation of collinear reactions over various energy hypersurfaces showed that excitation of the CS vibration results from release of energy as repulsion between the products. The yield is sharply dependent on the steepness of the interaction potential between the separating products and seems likely to vary with the impact parameters of the reactive collision.

Dissociation Energy of Boron Monofluoride from Mass-Spectrometric Studies

Gaseous equilibria involving BF, BF3, Ca, CaF, and CaF2 were studied by mass spectrometry in the range 1583° to 1734°K. The vapor species were produced in a graphite Knudsen cell containing a mixture of elemental boron and calcium fluoride, and they were identified from their characteristic mass spectra and ionization-efficiency curves. From ion-intensity measurements made at ionizing energies a few volts above threshold, the equilibrium constants and heats of several reactions involving BF (g) were evaluated. These results yield the standard heat of formation −27.5±3 kcal/mole for BF (g) and the dissociation energy, D0°, of 7.85±0.15 eV. The thermochemical dissociation energy of BF is significantly larger than a spectroscopic value obtained from linear extrapolation of the ground-state vibrational levels, but it agrees well with a value taken from a short extrapolation of the vibrational levels in the excited 1π state.

Absorption Spectrum of the ``Pink'' Afterglow of Nitrogen in the Vacuum Ultraviolet

The absorption spectrum of the short-lived ``pink'' afterglow in nitrogen was photographed in the vacuum ultraviolet from 1600 to 1150 Å. A large number of relatively intense absorption bands were observed. It is suggested that these may result from transitions between the ground state (X 1Σg+) and several excited electronic states (b 1IIu, b′ 1Σu+, and others) in which ground-state vibrational levels of the ground electronic state are populated to very high levels (up to about v″=20). It appears that more than 10% of the nitrogen molecules are excited to vibrational levels greater than v″=8.