arXiv subjects

Eisen C. Gross

Publications and source records attributed to Eisen C. Gross.

3 recordsLinked to original sources

arXiv2021

Re-evaluation of ortho-para-dependence of self-pressure broadening in the $v_1+v_3$ band of acetylene

Optical frequency comb-referenced measurements of self pressure-broadened line profiles of the R(8) to R(13) lines in the \thisband combination band of acetylene near 1.52$μ$m are reported. The analysis of the data found no evidence for a previously reported [Iwakuni et al. \textit{Phys. Rev. Letts.} \textbf{117}, 143902(5) 2016] systematic alternation in self pressure-broadened line widths with the nuclear spin state of the molecule. The present work brought out the need for the use of an accurate line profile model and a careful accounting for weak background absorptions due to hot-band and lower abundance isotopomer lines. The data were adequately fit using the quadratic speed-dependent Voigt profile model, neglecting the small speed-dependent shift. Parameters describing the most probable and speed-dependent pressure-broadening, most probable shift, and the line strength were determined for each line. Detailed modeling of the results of Iwakuni et al. showed that their neglect of collisional narrowing due to the speed-dependent broadening term, combined with the strongly absorbing data recorded and analyzed in transmission mode were likely the reasons for their results.

physics.chem-ph↗

arXiv2020

The 1.66 $μ$m Spectrum of the Ethynyl Radical, CCH

Frequency-modulated diode laser transient absorption spectra of the ethynyl radical have been recorded at wavelengths close to 1.66 $μ$m. The observed spectrum includes strong, regular, line patterns. The two main bands observed originate in the ground $\tilde{X}\,^2Σ^+$ state and its first excited bending vibrational level of $^2Π$ symmetry. The upper states, of $^2Σ^+$ symmetry at 6055.6 cm$^{-1}$ and $^2Π$ symmetry at 6413.5 cm$^{-1}$, respectively, had not previously been observed and the data were analyzed in terms of an effective Hamiltonian representing their rotational and fine structure levels to derive parameters which can be used to calculate rotational levels up to J = 37/2 for the $^2Π$ level and J = 29/2 for the $^2Σ$ one. Additionally, a weaker series of lines have been assigned to absorption from the second excited bending, (020), level of $^2Σ$ symmetry, to a previously observed state of $^2Π$ symmetry near 6819 cm$^{-1}$. These strong absorption bands at convenient near-IR laser wavelengths will be useful for monitoring CCH radicals in chemical systems.

physics.chem-ph↗

arXiv2018

Analysis of the $\tilde{A}-\tilde{X}$ bands of the Ethynyl Radical near 1.48$μ$m and Re-evaluation of $\tilde{X}$ State Energies

We report the observation and analysis of spectra in part of the near-infrared spectrum of C$_2$H, originating in rotational levels in the ground and lowest two excited bending vibrational levels of the ground $\tilde{X}\,^2Σ^+$ state. In the analysis, we have combined present and previously reported high resolution spectroscopic data for the lower levels involved in the transitions to determine significantly improved molecular constants to describe the fine and hyperfine split rotational levels of the radical in the zero point, $v_2=1$ and the $^2Σ^+$ component of $v_2=2$. Two of the upper state vibronic levels involved had not been observed previously. The data and analysis indicate the electronic wavefunction character changes with bending vibrational excitation in the ground state and provide avenues for future measurements of reactivity of the radical as a function of vibrational excitation.

physics.chem-ph↗