Ara Chutjian

Calculation of Predissociation Rates of the B 3Π0+u State of I2

A comparison of the purely radiative decay rates of vibrational levels of the B 3Π0+u state of I2 with total decay rates obtained from several independent lifetime measurements has indicated a significant amount of spontaneous predissociation of the B state. We present here a calculation of the observed relative predissociation rates by means of a model consisting of a repulsive 1u state which is coupled to the υ′J′ levels of the B state by rotational and electronic angular‐momentum terms neglected in the zeroth‐order Hamiltonian. The heterogeneous predissociation rate between a bound υ′J′ level and a continuum level at the same energy is calculated from Kronigs theory using exact wavefunctions for both levels. The dependence of this rate on the rotational level J′ is taken into account, together with the fractional population of the υ′J′ levels which were excited in the measurement of the total decay rates. Excellent agreement is found between the calculated and observed relative predissociation rates a...

Intensity Measurements in the B3Π0u+ − X 1Σ0+g System of I2

Equivalent width measurements were made on rotational lines in six vibrational bands in the B–X system of I2. All measurements were made photoelectrically. Calculations of the Doppler, natural, and collisional widths show the Doppler width to be 340 times larger than the combined natural and collisional width at 22°C. Measurement of the equivalent width at several path lengths for each line confirmed a pure Doppler curve of growth for the lines. From known spectroscopic data the line strengths gave a value for the square of the electronic contribution to the transition moment, and for the value of the total Einstein spontaneous emission rate from each υ′ to all υ″ with nonzero Franck–Condon factors. A comparison of these purely radiative decay rates with total decay rates measured by Chutjian, Link, and Brewer and by Davis and Grimes shows the presence of a significant amount of spontaneous predissociation of the B state to ground‐state 2P3/2 iodine atoms. In the absence of collisions approximately 66% of...

Electron impact excitation and assignment of the low-lying electronic states of N2O

Electron scattering spectra of CO2 are reported in the 7-10 eV energy-loss range, at energies of 0.2, 0.35, 0.6, 0.7 and 7.0 eV above threshold, and at a scattering angle of 90 degrees . Several new distinct overlapping continua with weak, diffuse bands superimposed are observed to lie in this energy-loss range. The experimental spectra are discussed in the light of ab initio configuration-interaction calculations by Winter et al (1973) of the vertical transition energies of CO2. The experimental spectra are shown to be consistent with excitations to the 3 Sigma u+, 1.3 Sigma u-, 1.3 Pi g, and 1.3 Delta u states of CO2.

Curves of Growth of Autoionizing Spectral Lines with Application to the 3s–4p Transition in Argon*

Curves of growth are calculated for autoionizing transitions having the Beutler–Fano form of absorption cross section. Both graphs and tabulated values of the curves are presented. The curve-of-growth analysis is applied to the 3s–4p transition in argon at 466 A. The line parameters Γ, q, and ρ2 obtained by fitting the theoretical and experimental equivalent widths are in good agreement with other high-resolution values. The curve-of-growth technique thus appears to be an attractive method for determining the parameters of autoionizing features. The application of this technique to make path-length or particle-density measurements in, for example, a King furnace or a plasma is also discussed.