Teresa J. Byers

High-resolution infrared spectroscopy of isotopic impurity Q1(0) transitions in solid parahydrogen

We have made a high‐resolution infrared spectroscopic study of the Q1(0) (v=1←0, J=0←0) vibrational transitions of the isotopic impurities D2 and HD in solid parahydrogen. Each impurity has a spectrum composed of ∼100 sharp lines spread over ∼0.4 cm−1. The linewidths vary, but are on the order of 10 MHz. These spectra make clear: (1) the infrared Q1(0) transitions of J=0 isotopic impurities are induced by the quadrupolar fields of nearby impurity J=1 molecules; and (2) the spectral pattern of strong Q1(0) lines is due to the splitting of the M‐orientational levels of J=1/J=0 o‐D2 or J=1/J=0 HD nearest‐neighbor (nn) impurity pairs. With the aid of several theoretical works, the strong lines in the D2 and HD spectra can be individually and unambiguously assigned as specific quantum state Q1(0) transitions of nn impurity pairs containing p‐D2/o‐D2 or o‐H2/o‐D2, and o‐H2/HD, respectively. The assigned transitions of nn impurity pairs containing o‐H2 are confirmed by combination differences which agree to with...

High-resolution laser spectroscopy of the Qv(0) transitions in solid parahydrogen

Our recent high-resolution laser spectroscopy of theQv(0) (υ=υ←0,J=0←0) transitions in solid parahydrogen is discussed. The systems studied include the fundamental vibrational bands of impurity D2 and HD, the first and second overtones of parahydrogen, and the charge-induced spectrum ofγ-ray irradiated parahydrogen. Additionally, Stark and stimulated Raman-gain spectroscopies are applied to the solid. The linewidths are as sharp as 2 MHz HWHM, which is highly unusual for a solid. Our spectra demonstrate a variety of physical phenomena, particularly theΔk = 0 selection rule, as well asJ = 1/J = 0 pair intermolecular interactions.

Direct measurement of the crystal field splitting of isolated J=1 impurities in solid parahydrogen

The crystal field splitting of single J=1 impurity orthohydrogen molecules in an otherwise pure J=0 parahydrogen crystal has been studied experimentally and theoretically over many years. We have measured this quantity directly from the fine structure of the Q3 (0) (v = 3← 0, J = 0← 0) overtone transition induced by J=1 hydrogen, in the near infrared using a Ti:sapphire laser. From our observed eight pairs of split spectral lines, we have determined the value Δ/k = [E(M=±1) − E(M=0)]/k = 0.0102 ± 0.0003 K including its sign. A straightforward numerical calculation based on ab initio calculations of the H2-H2 potential reproted by Mulder, van der Avoird, and Wormer gives Δ/k = 0.0116 K which is close to the experimental value. This suggests that the static and dynamic effects of phonons on the splitting may have been overestimated in the past.