G. L. Findley

Molecular Rydberg transitions. XII. Magnetic circular dichroism of methyl iodide

The absorption spectrum, the derivative spectrum, and the magnetic circular dichroism spectrum of methyl iodide are reported at various pressures in the energy range 48 000–59 000 cm−1 (i.e., the region of the 5p→6s Rydberg absorption bands). A method of determining the magnetic moment (μe) of a given electronic state is outlined, and the relative values of μe for the 5p→6s Rydberg vibronic bands are reported. These values lead to the identification of the four origin bands, the categorization of the pure electronic states with respect to angular momentum (in the linear molecule basis), and the assignment of all four of them. The MCD technique is a powerful tool for the assignment of vibrational bands: The value of μe and the sign of the MCD signature suffice to associate all bands to particular origins and to reveal detailed aspects of the vibronic coupling. Finally, the observed coupling of e vibrational and E electronic states of the symmetric top molecule provides insights into the nature of the vibro...

Molecular Rydberg states. XI. Quantum defect analogies between molecules and rare gases

The s and d Rydberg series of hydrogen iodide and methyl iodide are reported. These series are assigned using analogies to the corresponding series in xenon. It is shown that a comparison between molecular spectra and pertinent atomic data provides a facile assignment technique for molecular Rydberg spectra. Using the phase amplitude method, the Rydberg data are analyzed in an attempt to provide information on the residual atomic and molecular potentials and to categorize them qualitatively as attractive/repulsive, long range/short range. It is shown that, for l?2, the centrifugal barrier inhibits ingress of the Rydberg electron into the core and that the molecule is effectively spherically symmetric.

Molecular Rydberg transitions. XVIII. Vibronic doubling in methyl iodide

A massive vibronic coupling (dynamic Jahn–Teller) effect has been observed in the first s‐Rydberg transition of CD3I. The effect is conditioned more by energy‐denominator (i.e., near degeneracy) sizes than by matrix element (i.e., 〈H′〉?15 cm−1) sizes. The effect is observed in four different transitions of CH3I and CD3I where, by virtue of energy‐denominator variations, alterations of the effect by 2–3 orders of magnitude are observed and interpreted. A very simple model of the coupling is developed and is shown to be numerically powerful. Since the vibronic coupling takes place in an (Ωc,ω)‐spin–orbit coupling regime, the smallness of 〈H′〉 is surprising. It is shown that this small magnitude of 〈H′〉 is attributable to spin‐selection breakdown which the vibronic coupling in question must accomplish even in the (Ωc,ω) regime.

Laser‐power fluctuations: An analog signal‐correction technique

A simple and inexpensive analog technique which corrects spectroscopic signals for pulse‐to‐pulse fluctuations in the output power of an excitation laser is described. The technique is applicable to both linear and nonlinear spectroscopy and, in the latter case, requires no fast electronic function generator. This design yields an improved time‐constant characteristic which parallels the approach of the effective time constant toward RC. Furthermore, since this improvement does not require any preintegration, pulse shape information is preserved. A description of a photoacoustic (PA) spectrometer which incorporates the signal‐correction device and which relies on the photogalvanic effect for wavelength calibration is presented as an example. Finally, signal‐corrected PA spectra of the S1←S0 transition in azulene are presented.

Molecular Rydberg transitions. XX. Vibronic doubling in alkyl bromides

A doubling of absorption bands occurs in certain transitions associated with first s‐ and p‐Ryderg excitations in C2H5Br and C3H7Br. No such doubling occurs in the first d‐Rydberg or second s‐Rydberg excitation of C2H5Br. Furthermore, doubling is not evident in any Rydberg transition of CH3Br, CD3Br, or C2D5Br. The interpretation of this doubling phenomenon invokes vibronic coupling between Rydberg states of the same configuration. The active vibration is a C–H stretching mode ??3000 cm−1 and the presence of doubling is determined by coincidence (or near coincidence) of the intraconfigurational splitting and the frequency of the active vibrational mode.

Genetic coding: approaches to theory construction☆

Abstract A new approach to genetic coding theory, the generalized genetic code (GGC), is presented. It is shown how the GGC reunifies ambiguous codon assignments within the standard genetic code, thereby redefining genetic code universality in a modified form. An extensive survey of ambiguous codings (> 100 assignments) is presented as a critical test of the GGC and all assignments are successfully analyzed within the GGC Finally, the operative nature of biological contexts is investigated and discussed.

Molecular Rydberg transitions: Cyanogen chloride☆

Abstract The electronic absorption spectrum of cyanogen chloride has been investigated in the range 2200-1250 A. The first s -Rydberg transitions, X 1 Σ + → 3 Π 1 and X 1 Σ + → 1 Π 1 have been assigned, and analyzed to yield exchange and spin-orbit coupling parameters. The relative intensities of these two transitions have been shown to accord with an intermediate coupling situation. The π → π ∗ intravalence excitations, leading to 1.3 (Σ − , Δ and Σ + ) states, have been discussed. It has been shown that one or both of the 1 Σ − and 1 Δ states have bent geometries and that the 1 Σ + state is located (tentatively) at 79 755 cm −1 . Two σ → π ∗ π → σ ∗ states have been assigned, one at 56 340 cm −1 , the other at 74 450 cm −1 . The latter assignment is tentative, being largely based on observed vibronic interferences between the X 1 Σ + → 1 Π 1 transition and the 74 450 cm −1 transition. A considerable amount of vibrational oscillator strength and quantum defect data is presented.

Status report on the camd project

Abstract The LSU Center for Advanced Microstructures and Devices (CAMD) is a DOE-funded materials science and engineering laboratory which will include a normal-conducting compact electron storage ring optimized for the production of soft X-rays. The focus of CAMD is the fundamental study of processing and analysis technologies — including X-ray lithography — important to microstructure fabrication and electronic device development. Design details of the storage ring, which is being acquired commercially, are presented in this paper. In addition, the overall research mission of CAMD is described.

Molecular Rydberg transitions. The π → 4s transition of CICN

Abstract The first s-Rydberg transition of cyanogen chloride is discussed from the point of view of effective quantum numbers, oscillator strengths and the parameters of an intermediate-coupling model. It is shown that the ratio of oscillator strengths f (X → B)/ f (X → C) could be as low as 10 −2 and, on this basis, a set of first s-Rydberg assignments is proposed for CICN.

Molecular Rydberg transitions. XVI. MCD of CH3Br

Magnetic circular dichroism, first derivative (of absorption), and absorption spectra of methyl bromide are presented for the first s–Rydberg transition region, 55 000–61 000 cm−1. A straightforward analysis in terms of the ratios (MCD/derivative) of the signal amplitudes yields a unique identification of the first s–Rydberg states, 3E(1) and 1E(1). These identifications, in conjunction with oscillator strength ratios and an intermediate coupling model, lead to an assignment of the remaining first s–Rydberg states 3E(2) and 3E(0±). All of these assignments are corroborative of ones based on vibrational analyses and extrapolations [S. Felps, P. Hochmann, P. Brint, and S. P. McGlynn, J. Mol. Spectrosc. 59, 355 (1976)]. The power of MCD techniques in VUV Rydberg analyses is strikingly demonstrated.