Showing papers on "Excited state published in 1973"
TL;DR: In this paper, the authors developed the classical and quantum mechanics of a massless relativistic string, the light string, which is characterized by an action proportional to the area of the world sheet swept out by the string in space time.
580 citations
TL;DR: In this article, the authors discuss the experimental methods which are useful for studying these resonances, and review the results obtained by various investigators and discuss the configurations and other properties of resonances in atoms.
Abstract: Electrons colliding with atoms can form, at well-defined energies, compound states consisting of the target atom plus the incident electron. The compound states, which are also called "resonances" or "temporary negative ions," often dominate electron collision processes. In this review we discuss the experimental methods which are useful for studying these resonances, and review the results obtained by various investigators. We list the energies and the widths of resonances for H, He, Ne, Ar, Kr, Xe, Li, Na, Hg, and O. The configurations and other properties of resonances in atoms are discussed. Whenever applicable, results are presented in the form of tables and energy level diagrams.
563 citations
TL;DR: In this paper, a review of the available information on diphenyl polyenes is presented and a correlation of the oscillator strength of the fluorescence transition as deduced from the emission lifetime with the separation of the low energy excited states for a number of polyenes are noted.
Abstract: Optical absorption and emission spectra at liquid helium temperatures of solutions of all‐trans‐1,8‐diphenyloctatetraene in single crystals of bibenzyl and polycrystalline n‐paraffin matrixes are presented which show an excited singlet state at a lower energy than the 1Bu state responsible for the strong absorption of all linear polyenes. The transition from the ground state to this level has an oscillator strength of about 0.05. The location of this low energy weak transition removes a number of discrepancies between the expected and observed fluorescence properties of diphenyloctatetraene. The observed vibronic pattern is consistent with the Raman spectrum which is also reported. Substantial indirect evidence is presented which indicates that many, and perhaps all, linear polyenes have a similar ordering of excited states. A review of the available information on diphenylpolyenes is presented. A correlation of the oscillator strength of the fluorescence transition as deduced from the emission lifetime with the separation of the low energy excited states for a number of polyenes is noted. The implications for the photochemistry of linear polyenes including the visual chromophores are pointed out.
341 citations
TL;DR: Transition rate equations for atomic hydrogen were solved to obtain coefficients for population of excited levels and for ionization and recombination in this paper, and the results were based upon more accurate transition rates, cover a wider range of plasma parameters, and are obtained by a more general solution of the rate equations than previously available compilations.
Abstract: Transition rate equations for atomic hydrogen are solved to obtain coefficients for population of excited levels and for ionization and recombination. The results are based upon more accurate transition rates, cover a wider range of plasma parameters, and are obtained by a more general solution of the rate equations than previously available compilations. Diagnostic applications for laboratory plasmas are discussed.
302 citations
TL;DR: In this paper, a comparison of the spectra of metals and their oxides reveals large differences between the chemical shifts in Auger and photoelectron lines, and an explanation is proposed which is based upon the difference in polarization energy between the double-hole state produced by the Auger electron emission and the singlehole state which results from the photo-electron emission.
219 citations
TL;DR: In this paper, the ground state and excited energy levels of the generalized anharmonic oscillator defined by the Hamiltonian Hm = − d2/dx2+x2+ λx2m, m = 2,3, …, have been calculated using the Hill determinants.
Abstract: The ground state as well as excited energy levels of the generalized anharmonic oscillator defined by the Hamiltonian Hm = − d2/dx2+x2+ λx2m, m = 2,3, …, have been calculated nonperturbatively using the Hill determinants. For the λx4 oscillator, the ground state eigenvalues, for various values of λ, have been compared with the Borel‐Pade sum of the asymptotic perturbation series for the problem. The agreement is excellent. In addition, we present results for some excited states for m = 2 as well as the ground and the first even excited states for m = 3 and 4. The behaviour of all the energy levels with respect to the coupling parameter shows a qualitative similarity to the ground state of the λx4 oscillator. Thus the results are model independent, as is to be expected from the WKB approximation. Our results also satisfy the scaling property that en(m)(λ)/λ1/(m+1) tend to a finite limit for large λ, and always lie within the variational bounds, where available.
206 citations
TL;DR: In this paper, the problem of electron-phonon interaction for a pseudo-one-dimensional model of photoemission is discussed and the approximations necessary for a random-walk description of the propagation of the electron in the final state to be valid are given.
Abstract: The previous microcoscopic models of photoemission are developed and reformulated in order to include inelastic scattering effects. A general expression is given for the photocurrent and its energy distribution (EDC). The problem of inelastic scattering is more thoroughly discussed in the case of electron-phonon interaction for a pseudo-one-dimensional model. The approximations necessary for a random-walk description of the propagation of the electron in the final state to be valid are given. The microscopic formulation is then used to discuss phenomenological models such as the step model. It is shown that, in general, this model is not a good picture since one cannot separate simply the optical-transition step from the propagation of the excited electron and its escaping into the vacuum. In particular, even in the absence of inelastic effects, it is impossible to make a general prediction about the degree of accuracy with which the EDC may reproduce the optical joint density of states of the semi-infinite solid. Finally the paper discusses what type of information about the solid may be reasonably extracted from EDC measurements as a function of the energy of the primary excited state. It is concluded that the best conditions are met for uv and x-ray photoemission for which the elastic EDC should give information about the occupied surface states (uv) and bulk density of states (x ray).
181 citations
TL;DR: In this paper, a quantum-mechanical model for the process by which an atom is excited or ionized as it is sputtered from a metal surface was developed, where the probability of excitation was given by R = (A/ΔE)2(hv/aΔ E)n, where A is the binding energy of a surface atom before sputtering, v is its average velocity after sputtering and Δ E the excitation energy.
176 citations
TL;DR: In this paper, the visible fluorescence of the SiF radical in SiF4 gas irradiated by the pulsed output of a CO2 laser leads to the conclusion that the molecules are dissociated into electronically excited fragments by the action of the intense laser field.
Abstract: Observation of the visible fluorescence of the SiF radical in SiF4 gas irradiated by the pulsed output of a CO2 laser leads to the conclusion that the molecules are dissociated into electronically excited fragments by the action of the intense laser field. A clear distinction is observed between the fluorescence produced through this process and that associated with thermalization of the incident energy.
174 citations
TL;DR: In this article, the authors investigated the effect of vibronic perturbation of the ground state relative to that of the excited state on the induced transition dipole moment and found that the vibronic coupling between Born-Oppenheimer states via nuclear momenta, for which such a cancellation does not occur, tends to contribute measurably to induced transition moment, contrary to what usually is assumed.
Abstract: The Herzberg‐Teller theory of vibronic intensity borrowing is reinvestigated A potentially serious deficiency is found in the conventional approximation scheme based on neglecting vibronic perturbation of the ground state relative to that of the excited state Simple theoretical models are studied and show systematic cancellation of the lowest‐order induced transition dipole moment if both vibronic perturbations are included As a result the vibronic coupling between Born‐Oppenheimer states via nuclear momenta, for which such a cancellation does not occur, tends to contribute measurably to the induced transition moment, contrary to what usually is assumed Two methods to distinguish between Herzberg‐Teller‐type (HT) and Born‐Oppenheimer‐type (BO) contributions are discussed, namely the absorption‐emission asymmetry and the isotope effect The former results from interference between HT and BO terms, which is usually constructive in absorption and destructive in emission; the latter is due to the fact tha
160 citations
TL;DR: In this paper, the solvent shift effect is caused by a weak interaction between the solute and surrounding solvent molecules and is best treated using quantum-mechanical perturbation theory that allows it to be divided into electrostatic type interactions and dispersion interactions.
Abstract: Publisher Summary The spectrum of a substance in a solution is changed compared to its spectrum in the vapor state. Solvent-shift effect is caused by a weak interaction between the solute and surrounding solvent molecules. The change in energy of the system because of this interaction will differ depending on if the solute molecule is in its ground or excited state and consequently there will be the change in excitation energy observed experimentally. The solvent–solute interaction, being weak, is best treated using quantum–mechanical perturbation theory that allows it to be divided into electrostatic type interactions and dispersion interactions. The electrostatic type interactions relate the solvent shift to the change in dipole moment and polarizability of the solute molecule on excitation from its ground state to its excited state and thus, can give experimental values-albeit once removed-of excited-state dipole moments and polarizabilities. The order-of-magnitude values for excited-state dipole moments can be obtained from solvent shift data. All solvent-shift theories are based on the assumption that solvent and solute molecules are sufficiently well separated that overlap of electronic distribution can be neglected. The chapter proves with the help of calculations that Abe's theory and the reaction-field method differ by very little in the final analysis. The solvent-shift data can also be used to obtain the order of magnitude estimates of excited-state dipole moments.
TL;DR: In this article, the photostability of quinazolines, pyrimidines, pyrazines, benzotriazoles, and benzophenones with an o-hydroxyphenyl group in ortho position to a ring nitrogen or a carbonyl group was investigated.
Abstract: Photostability, defined as the inverse of the quantum yield of a photochemical reaction, is assumed to be proportional to the rate of internal conversion. The rate of internal conversion is inversely proportional to the energy difference between the first excited state and the ground state. In intramolecularly hydrogen‐bonded π systems, the photoexcited enol form rearranges itself to an excited keto form. SCF LCAO MO calculations indicate that the energy difference between the first excited state and the ground state is smaller in the keto form than in the enol form. Experiments are reported in support of these theoretical considerations. Weak, strongly red‐shifted fluorescence is observed at 77°K for several photostable quinazolines, pyrimidines, quinolines, pyrazines, benzotriazoles, and benzophenones with an o‐hydroxyphenyl group in ortho position to a ring nitrogen or a carbonyl group. For some compounds a moderately red‐shifted fluorescence is observed as well. No phosphorescence is detected. None of the compounds fluoresce at room temperature. When intramolecular hydrogen bonding is destroyed by, e.g., methylation, the compound shows phosphorescence and moderately red‐shifted fluorescence. With data from the literature, the increase in photostability due to enol‐keto tautomerism in the excited state is estimated. The increase agrees well with the experimental results.
TL;DR: The current status of the theory of the electronic structure of polymers containing conjugated bonds is reviewed in this article, where an exact solution of the wave functions of the ground and excited states is found and the exact excitation spectrum is analyzed.
Abstract: The current status of the theory of the electronic structure of polymers containing conjugated bonds is reviewed. Compounds having conjugated bonds have a number of remarkable physical properties, and they occupy a central point in quantum-mechanical studies. The energy of the first optical transition as a function of the molecular length shows unusual behavior. As the molecule is lengthened, the energy of the first transition approaches a finite value called the gap. Hence such a polymer is a semiconductor. A first attempt to explain the gap was based on the hypothesis of spontaneous alternation of bond lengths. The review presents this hypothesis and subjects it to a thorough critique. It has recently been shown that the mechanism that gives rise to the gap in these systems is interaction of electrons and an associated Mott metal-dielectric transition. This conclusion was first based on the unrestricted Hartree-Fock method, and later upon exact solutions for the one-dimensional problem. The article reviews these studies. Polymers with conjugated bonds also show non-trivial magnetic properties, in spite of their lack of d and f electrons. The magnetic properties of these compounds can be described on the basis of the one-dimensional Hamiltonian of Hubbard. Here an exact solution of the wave functions of the ground and excited states is found and the exact excitation spectrum is analyzed. The ground state of these polymers proves to be antiferromagnetic at absolute zero. The spin-wave spectrum begins at zero. Hence these systems show appreciable paramagnetism at finite temperatures. This review analyzes the relation of the paramagnetic susceptibility and the intensity of the EPR signal to the temperature and the polymer length. In conclusion, the review lists problems and questions in the theory of the electronic structure of conjugated polymers that await solution.
TL;DR: In this article, the infrared and visible spectra of gaseous oxygen have been examined at temperatures around 90°K using a long path absorption cell, and the visible absorption of (O2)2 corresponds to the 1 Δg (ν=0)+1 Δg(ν=1) ←3 Σg−(ν = 0) simultaneous transition.
Abstract: The infrared and visible spectra of gaseous oxygen have been examined at temperatures around 90°K using a long path absorption cell. At all temperatures the infrared and visible spectra show a broad band which can be assigned as collision‐induced absorption. However, at low temperatures small but discrete features appear with integrated intensities dependent on the square of the gas density. These features are assigned to bound state van der Waals molecules of the type (O2)2. The visible absorption of (O2)2 studied corresponds to the 1 Δg (ν=0)+1 Δg(ν=1) ←3Σg−(ν=0) simultaneous transition. The part of the spectrum attributed to bound dimers shows a progression of eight fine structure bands superimposed on the broad simultaneous transition absorption. The fine structure has been assigned to combinations of electronic and vibrational transitions involving the stretching mode of the van der Waals bond of (O2)2. In the ground state each oxygen molecule is in the 3 Σg−(ν=0) state, while in the excited state on...
TL;DR: In this article, a tunable ultraviolet laser, summation of dye plus ruby, provided 7 nsec pulses with less than 1 A wavelength spread, and decay rates, extrapolated to zero pressure, increase rapidly with increasing vibrational energy.
Abstract: Predissociation, quenching and energy transfer have been studied for single vibrational levels of the first excited singlet state of formaldehyde (1A2). A tunable ultraviolet laser, summation of dye plus ruby, provided 7 nsec pulses with less than 1 A wavelength spread. Fluorescence decay lifetimes were measured as a function of pressure. The decay rates, extrapolated to zero pressure, increase rapidly with increasing vibrational energy. A hundredfold increase in rate is observed for 4000 cm−1 in D2CO. The variation of rate with the particular combination of normal modes excited in comparatively small. The effect of deuteration is marked; H2CO decays about twenty times faster than D2CO. We believe that for the energy range studied the only mechanism of radiationless decay compatible with the energy level structure of formaldehyde and with the lifetime observations is internal conversion to high vibrational levels of the ground state which are broadened by unimolecular dissociation. The rates measured for ...
TL;DR: In this article, a defect model for the float-zone intrinsic silicon irradiated with reactor neutrons up to the total fluence was established, and the anisotropy of the $g$ tensor and its continuous variation with temperatures were also discussed in terms of simple linear-combination-of-atomic-orbitals molecular orbitals and of the experimental results on the resonant wave function.
Abstract: EPR studies are carried out for the float-zone intrinsic silicon irradiated with reactor neutrons up to the total fluence ${10}^{18}$ n/${\mathrm{cm}}^{2}$. Details of the ${\mathrm{Si}}^{29}$ hyperfine structure and of the $g$ tensor in the $P\ensuremath{-}1$ spectrum are observed with respect to temperature from 77 to 350\ifmmode^\circ\else\textdegree\fi{}K. The anisotropy of the $g$ tensor and its continuous variation with temperatures are also discussed in terms of simple linear-combination-of-atomic-orbitals molecular orbitals and of the experimental results on the resonant wave function. In particular, the motional effect due to the electron-hopping between equivalent defect sites proposed by Nisenoff and Fan is not supported by these experiments, but an unusual thermal effect is observed in which the resonant-electron wave function is an average of both a ground and excited states, with the relative populations being proportional to the Boltzmann factor. The resonance properties of the pure ground state and pure excited state differ, which causes the $g$ and $A$ tensors to continuously vary with temperature and brings about a line broadening and narrowing in the hyperfine satellites as well as in the central lines. The line width broadening of the hyperfine lines is discussed on the basis that it is mainly due to transitions between the ground and excited electronic states. Based on the present results, a defect model for this center is established: a negative charge state of a nonplanar five-vacancy cluster.
TL;DR: In this article, it is proposed that the dynamic electron polarization is due to the optically spin polarized triplets of the parent quinones and their subsequent hydrogen abstraction reaction with retention of polarization in the resultant semiquinone radicals.
Abstract: Electron spin resonance emission was observed from some photochemically produced semiquinone radicals in liquid isopropanol. It is proposed that the dynamic electron polarization is due to the optically spin polarized triplets of the parent quinones and their subsequent hydrogen abstraction reaction with retention of polarization in the resultant semiquinone radicals. Theoretical calculations have been carried out using typical zero field parameters for aromatic triplet molecules and the established assumption that the intersystem crossing rates to the three sublevels are unequal. Calculations reveal significant spin polarization of the triplets randomly oriented in an arbitrary magnetic field. Further treatment shows that when the triplet depolarization via relaxation is comparable to the chemical hydrogen abstraction rate, the resultant radical retains the polarization and is thus in the emissive mode.
TL;DR: In this article, the authors measured delayed coincidences between electrons of incident energy about 80 eV scattered inelastically from helium and photons from excited $3^{1}P$ and $2^{1]P$ states and compared the atomic radiation patterns with those predicted by the Born approximation.
Abstract: Angular correlations were measured by delayed coincidences between electrons of incident energy about 80 eV scattered inelastically from helium and photons from excited $3^{1}P$ and $2^{1}P$ states. From the angular correlation in each case we deduce the ratio of the differential cross sections for exciting the magnetic sublevels of the excited state and the phase between the corresponding excitation amplitudes. We compare the atomic radiation patterns with those predicted by the Born approximation.
TL;DR: In this article, the authors developed formulas for calculating spectroscopic amplitudes for emission or transfer of α-particles in the framework of the harmonic-oscillator shell model with SU(3) classification.
TL;DR: In this paper, the van der Waals dimer Kr2 has been photographed in the region 1050-1260 A by a 6.65 m spectrograph with the argon continuum as background source.
Abstract: The vacuum ultraviolet absorption spectrum of the van der Waals dimer Kr2 has been photographed in the region 1050–1260 A by a 6.65 m spectrograph with the argon continuum as background source. Eight band systems, four well‐developed and four rather fragmented, are observed. Vibronic analyses of the former four systems reveal that their upper states are correlated to separated atom limits in which one Kr atom is excited to various levels of configuration 4p55s. Upper molecular state designations and dissociation limits are discussed. The four fragmented band systems are energetically close to various KrI levels of configuration 4p55p. A similar study of a mixture of argon and krypton yields five groups of diffuse bands attributed to ArKr; two of these band groups are close to KrI resonance lines. The ground electronic state of Kr2 supports 16 bound vibrational levels of which nine (ν″ = 0–8) are involved in the observed vibronic structure and the other seven inferred from an extrapolation procedure based ...
TL;DR: In this article, the decay rates for particle emission and exciton-exciton interactions were derived from the probabilities per unit time of particle-particle and hole-hole collisions inside the nucleus.
TL;DR: In this paper, the energy and angular dependences of the cross section ratios are used to identify the nature of the excited states, and two transitions with maxima at 3.22 and 4.91 eV are identified as singlet-->triplet transitions.
Abstract: The electron impact excitation of 1,3-butadiene has been studied experimentally at impact energies of 20, 35, and 55 eV and scattering angles from 10° to 85°. The energy and angular dependences of the cross section ratios are used to identify the nature of the excited states. Two transitions with maxima at 3.22 and 4.91 eV are identified as singlet-->triplet transitions. Comparison with theoretical calculations indicates that these are due to the 13Bu and 13Ag states, respectively. Their significance for the photochemistry of this molecule is discussed. The optically allowed X-tilde 1Ag --> 11Bu(N --> V1) transition is observed with a maximum at 5.92 eV. An additional transition appears between 6.9 and 7.8 eV with vibrational features at 7.09, 7.28, and 7.46 eV. The optical absorption in this region was originally attributed to a 1A1 state of the s -cis molecule and subsequently to a Rydberg state or to a 1Ag state of the s -trans molecule. On the basis of intensity arguments and the angular dependence of the cross section ratios, we suggest that it may instead be due to the X-tilde 1Ag --> 21Bu transition of the s -trans molecule. Rydberg transitions are observed at 8.00 and 8.18 eV. Two broad transitions are also seen beyond the first ionization potential with maxima at 9.50 and 11.00 eV. The results of this study are in good agreement with recent ab initio configuration interaction (CI) calculations, and give support to the analysis of the valence excited states in terms of a "molecules-in-molecules" approach. This is consistent with recent interpretations of the resonance energy and reactivity of this molecule and differs from the older classic model of extensive delocalization in the pi electron system.
TL;DR: In this article, a unique combination of properties in the host crystal BaY2F8 has made it possible to obtain laser emission from the Dy3+ ion at 3.022 μ.
Abstract: A unique combination of properties in the host crystal BaY2F8 has made it possible to obtain laser emission from the Dy3+ ion at 3.022 μ. The laser line lies close to the electronic transition from the lowest level of the 6H13/2 excited state at 3520 cm−1 to a ground manifold level at 216 cm−1, but the oscillation frequency is shifted by 5 cm−1 due to overlapping vibronic lines. The intensity of Dy3+ emission is enhanced by energy transfer from Er3+, Yb3+, Tm3+, and Ho3+. The restrictions imposed on the multiphonon decay rates for the operation of a Dy3+ laser at 3 μ are discussed. A comparison of radiative and nonradiative relaxation rates for rare‐earth ions in BaY2F8 indicates that an extension of laser emission to beyond 4 μ is unlikely.
TL;DR: In this paper, the energy levels of the 3p5 2p1(1/2)4s[1( 1/2)]2 1s5 in Paschen's notation have been calculated using the dispersion formula for air adopted by the International Astronomical Union.
Abstract: The spectrum of Ar i has been reobserved with grating spectrographs in large parts of the photographic range. The energy levels have been calculated taking into consideration interferometric and grating observations made since the publication of Atomic Energy Levels (1949) and by use of the dispersion formula for air adopted by the International Astronomical Union. Four ground-level combinations between 1066 and 876 A have been carefully measured on spectrograms taken with the 10.7-m vacuum spectrograph at the National Bureau of Standards; two in the second and two in the fourth order. They give for the lowest excited level, 3p5 (2P1(1/2))4s[1(1/2)]2 1s5 in Paschen’s notation), the value 93143.76 ± 0.05 cm−1 relative to the ground level zero. By use of this level, the 3p5nl level system as a whole has been accurately located relative to the ground level. From the levels, 34 lines in the vacuum ultraviolet between 1066 and 792 A have been calculated according to the combination principle. Between 894 and 806.8 A, these should be accurate to ± 0.0004 A or better, whereas for the 1066- and 1048-A lines and several lines below 806.8 A, the limits of error are somewhat larger. From interferometrically determined values of levels of types n s (n > 5) and n d (n > 3) accurate combinations with those of type 4p in the 10068–4768-A range have been calculated. The (3p5 2P1(1/2)) ionization energy, referred to the ground state of Ar ii, is 127109.80 ± 0.10 cm−1.
TL;DR: Fluorescence spectra and fluorescence quantum yields have been determined for a wide variety of alkanes, cycloalkanes, and polycycloalkane excited at 147 and 165 nm.
Abstract: Fluorescence spectra and fluorescence quantum yields have been determined for a wide variety of alkanes, cycloalkanes, and polycycloalkanes excited at 147 and 165 nm. Correlations between emission characteristics and molecular structure are noted and discussed.
TL;DR: In this paper, temperature dependence measurements of the decay times of the observed charge transfer luminescence of three ruthenium (II) complexes indicate a manifold of decaying excited levels in thermal equilibrium.
Abstract: Temperature dependence measurements of the decay times of the observed charge‐transfer luminescence of three ruthenium (II) complexes indicate a manifold of decaying excited levels in thermal equilibrium. Relative energies and decay constants for each level have been derived from the data for the tris(2, 2′‐bipyridine)ruthenium(II) and tris(4, 4′‐diphenyl‐2, 2′‐bipyridine)ruthenium(II) cations and for cis‐dicyanobis(2, 2′‐bipyridine) ruthenium(II). An electronic coupling model has been proposed that satisfactorily rationalizes the experimental results and allows the levels to be symmetry labeled.
TL;DR: In this article, an analytical model for the spectra due to excitation of a core electron in metal with an incomplete shell was proposed. But the model assumes that the incomplete shell is treated as a nondegenerate localized state interacting with conduction band through the s − d mixing.
Abstract: Analytic features of the spectra due to excitation of a core electron in metal with an incomplete shell are studied with a simple model. The incomplete shell (denoted by d state, representatively) is treated as a nondegenerate localized state interacting with conduction band through the s – d mixing. It is assumed that in the initial state of the absorption the unoccupied d level is well above the Fermi energy e F while in the final states the d level of the excited atom is lowered down to e d due to the core hole left behind. When e d > e F , the singular absorption edge appears at \(\tilde{\varepsilon}_{\text{F}}\) as expected, with an antiresonance around \(\tilde{\varepsilon}_{d}\). When e d < e F , the singular absorption edge appears at \(\tilde{\varepsilon}_{d}\), the Fermi level threshold being blurred out by the life time effect of the d hole. Emission spectra are also calculated. The results are compared qualitatively with experimental data.
TL;DR: Shibuya and McKoy as mentioned in this paper extended the equations of motion with respect to the ground state particle-hole densities and showed how to include the effects of two-particle-hole components in excited states.
Abstract: The equations‐of‐motion method is discussed as an approach to calculating excitation energies and transition moments directly. The proposed solution [T. Shibuya and V. McKoy, Phys. Rev. A 2, 2208 (1970)] of these equations is extended in two ways. First we include the proper renormalization of the equations with respect to the ground state particle‐hole densities. We then show how to include the effects of two‐particle‐hole components in excited states which are primarily single‐particle‐hole states. This is seen to be equivalent to a single‐particle‐hole theory with a normalized interaction. Applications to various diatomic and polyatomic molecules indicate that the theory can predict excitation energies and transition moments accurately and economically.
TL;DR: In this article, the population distribution of the (v,J) levels of the ground state was measured by spectroscopically analyzing the white light and laser-induced fluorescence excited in a nozzle beam of Na2 molecules.
Abstract: By spectroscopically analyzing the white light and laser‐induced fluorescence excited in a nozzle beam of Na2 molecules, we have measured the population distribution of the (v,J) levels of the ground state. The Na2 molecules are produced in nozzle beams with various stagnation pressures (50–240 torr) of alkali metal and with nozzles of different throat diameters (0.12–0.50 mm). We find at a stagnation pressure of 50 torr and a nozzle diameter of 0.5 mm a Boltzmann distribution characterized by a vibrational temperature of 153 ± 5°K and a rotational temperature of 55± 10°K. Beams under different stagnation conditions have essentially the same internal state distribution. Studies of K2 dimers produced in a nozzle beam with various stagnation pressures (20–300 torr) and a 0.25 mm nozzle throat diameter also show cooling in both vibrational and rotational modes. A search is made for atomic fluorescence arising from the photodissociation of dimers in high vibrational levels of the ground state. No evidence is ...