Franck-Condon factors and observed band strength distribution in the vibrational structure of the Ag_2 D-X band system

Potential curves for the X_1Σ_g^+ and D_1Σ_u^+ states of three diatomic silver isotopomers, ^(107)Ag_2, ^(107)Ag^(109)Ag and ^(109)Ag_2, were determined from the best available molecular constants by the Rydberg-Klein-Rees method. From these potentials, Franck-Condon factors and band-origin wave numbers were computed, and the reliability of the obtained values was verified by comparison with the observed band strength distribution and the measured band origin positions in a previously recorded D-X spectrum. The ratios of the Franck-Condon factors to those of corresponding isotopic bands were found to be very close to unity, revealing only a very small isotopic effect on the Franck Condon factors of Ag_2 D-X bands. The isotopic shifts of the calculated band origins agree well with previously measured displacements of band heads

Franck–Condon factors and observed band strength distribution in the vibrational structure of the Ag2 D-X band system

TPotential curves for the X1Sg+ and D1Su+ states of three diatomic silver isotopomers, 107Ag2, 107Ag109Ag and 109Ag2, were determined from the best available molecular constants by the Rydberg–Klein–Rees method. From these potentials, Franck–Condon factors and band-origin wavenumbers were computed, and the reliability of the obtained values was verified by comparison with the observed band strength distribution and the measured band origin po¬sitions in a previously recorded D-X spectrum. The ratios of the Franck–Con¬don factors to those of corresponding isotopic bands were found to be very close to unity, revealing only a very small isotopic effect on the Franck–Condon factors of Ag2 D-X bands. The isotopic shifts of the calculated band origins agree well with previously measured displacements of band heads

Low energy elastic and electronically inelastic electron scattering from biomolecules.

Reactions initiated by collisions with low-energy secondary electrons has been found to be the prominent\ud mechanism toward the radiation damage on living tissues through DNA strand breaks. Now it is widely accepted\ud that during the interaction with these secondary species the selective breaking of chemical bonds is triggered\ud by dissociative electron attachment (DEA), that is, the capture of the incident electron and the formation\ud of temporary negative ion states [1,2,3]. One of the approaches largely used toward a deeper understanding\ud of the radiation damage to DNA is through modeling of DEA with its basic constituents (nucleotide bases,\ud sugar and other subunits). We have tried to simplify this approach and attempt to make it comprehensible\ud at a more fundamental level by looking at even simple molecules. Studies involving organic systems such as\ud carboxylic acids, alcohols and simple ¯ve-membered heterocyclic compounds are taken as starting points for\ud these understanding. In the present study we investigate the role played by elastic scattering and electronic\ud excitation of molecules on electron-driven chemical processes. Special attention is focused on the analysis of\ud the in°uence of polarization and multichannel coupling e®ects on the magnitude of elastic and electronically\ud inelastic cross-sections. Our aim is also to investigate the existence of resonances in the elastic and electronically\ud inelastic channels as well as to characterize them with respect to its type (shape, core-excited or Feshbach),\ud symmetry and position. The relevance of these issues is evaluated within the context of possible applications\ud for the modeling of discharge environments and implications in the understanding of mutagenic rupture of DNA\ud chains. The scattering calculations were carried out with the Schwinger multichannel method (SMC) [4] and\ud its implementation with pseudopotentials (SMCPP) [5] at di®erent levels of approximation for impact energies\ud ranging from 0.5 eV to 30 eV.\ud References\ud [1] B. Boudai®a, P. Cloutier, D. Hunting, M. A. Huels and L. Sanche, Science 287, 1658 (2000). [2] X. Pan, P.\ud Cloutier, D. Hunting and L. Sanche, Phys. Rev. Lett. 90, 208102 (2003). [3] F. Martin, P. D. Burrow, Z. Cai,\ud P. Cloutier, D. Hunting and L. Sanche, Phys. Rev. Lett. 93, 068101 (2004). [4] K. Takatsuka and V. McKoy,\ud Phys. Rev. A 24, 2437 (1981); ibid. Phys. Rev. A 30, 1734 (1984). [5] M. H. F. Bettega, L. G. Ferreira and\ud M. A. P. Lima, Phys. Rev. A 47, 1111 (1993)

Differential Cross Sections and Cross-Section Ratios for the Electron-Impact Excitation of the Neon 2p⁵3s Configuration

Electron-impact differential cross-section measurements for the excitation of the 2p53s configuration of Ne are reported. The Ne cross sections are obtained using experimental differential cross sections for the electron-impact excitation of the n = 2 levels of atomic hydrogen [Khakoo et al., Phys. Rev. A 61, 012701-1 (1999)], and existing experimental helium differential cross-section measurements, as calibration standards. These calibration measurements were made using the method of gas mixtures (Ne and H followed by Ne and He), in which the gas beam profiles of the mixed gases are found to be the same within our experimental errors. We also present results from calculations of these differential cross sections using the R-matrix and unitarized first-order many-body theory, the distorted-wave Born approximation, and relativistic distorted-wave methods. Comparison with available experimental differential cross sections and differential cross-section ratios is also presented

Reinvestigation of the electronic transition moment function of the BO B^2Σ^+–X^2Σ^+ band system

The relative intensities of nine emission bands associated with the v′=0v′=0 and 1 vibrational levels of the B^2Σ^+–X^2Σ^+ system of the BO molecule are measured. The integrated relative intensities of the (0, 0), (0, 1), (1, 0) and (1, 1) bands are measured for the first time in this work. The ratios of observed intensities for bands originating from the same upper vibrational level, together with the Franck–Condon factors, q_(v′v″), and r-centroids, r_(v′v″), based on Rydberg–Klein–Rees potential energy curves, derived from the best available spectroscopic data for the B^2Σ^+ and X^2Σ^+ states of ^(11)B^(16)O and ^(10)B^(16)O, are used to reinvestigate the dependence of the electronic transition moment (ETMF), R_e(r), on internuclear distance, r, for the BO B^2Σ^+–X^2Σ^+ band system. The linear expression R_e(r_(v'vv')=k(−1+1.393r_(v′v″)), where k is an arbitrary constant, is derived from our data to describe the measured r-centroid variation of the ETMF for this system over the range 1.23Å≤r≤1.40Å of internuclear distance. The form of this expression is suitable for directly comparing with previous work, and we find excellent agreement with the BO B–X relative ETMF of Robinson and Nicholls [Intensity measurements on the CO^+ comet tail, and the BO α and β molecular band systems. Proc. Phys. Soc. 1960;75:817–25]. Recent radiative-lifetime measurements of the ^(11)BO B state have allowed us to normalize our ETMF to absolute units: Re(r_(v′v″))=0.4672r_(v′v″)−0.3354 (electric dipole moment atomic units), where r_(v′v″) is in Å

Radiative transition parameters of the 107,109 Ag_2C^1∏_u-X^1∑_g^+ band system

The relative band strengths of several absorption bands of the Ag2C1∏u-X1∑g+ system are measured for the first time. Ratios of observed strengths for bands with common lower vibronic levels are compared with theoretically predicted absorption band oscillator strengths, which we computed by numerically solving the radial Schrödinger equation for the vibrational wave functions, ψυ′ and ψυ″ of the 107,109 Ag2C1∏u-X1∑g+ band system, using Rydberg–Klein–Rees potential energy curves and a suitable choice for the electronic transition moment function. This resulted in a useful set of radiative transition parameters for a large matrix of Ag2 C–X bands. The functional form of the electronic transition moment required by the observed band strength ratios forces good agreement between the observations and diatomic molecular theory. Since the function is highly nonlinear, the commonly applied r-centroid approximation is invalid, and numerical integration of ʃ Ψv'*Re(r)Ψv' dr had to be performed instead. As a final check on the reliability of our results, we find good agreement between the experimentally measured displacements of band heads for the 107,107 Ag2 and 109,109 Ag2 isotopologues and the corresponding isotopic shifts of our calculated band origins

Experimental and predicted Ag_2 B^1∏_u-X^1∑^+_g absorption band strengths

Relative intensities in the absorption spectrum of the B^1∏_u–X^1∑^+_g band system of diatomic silver are measured for the first time. Analysis of these measurements is performed using Rydberg–Klein–Rees potential curves derived from the best available vibrational and rotational constants for this band system. Comparison of measured and calculated absorption band strength ratios for eleven vibrational bands reveals that the relative electronic transition moment function (ETMF) of the Ag_2 B–X system has a negative slope and decreases by ≈ 40% over the 2.43–2.58 Å range of internuclear distance. The ETMF shows some nonlinear structure; however, the empirical error bars suggest that a linear model is appropriate, thus allowing the r-centroid approximation as a simplification in our analysis

Franck–Condon factors and observed band strength distribution in the vibrational structure of the Ag2 D-X band system - Supplementary material

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Franck–Condon factors and observed band strength distribution in the vibrational structure of the Ag2 D-X band syste