Stephen C. Foster

Observation of the ν3 fundamental band of HCO

The ν3 (C–O stretching) band of HCO+ has been detected using a tunable diode laser spectrometer and a liquid nitrogen cooled hollow cathode absorption cell. Eight lines in the R branch, ranging from R(6) to R(17) were measured with an accuracy of 0.001 cm−1. Combining these data in a least‐squares fit with the previously measured v3=1, J=1←0 microwave transition, the following parameters were determined: ν0=2183.9496 cm−1, B=44 299.904(10) MHz, and D=82.96(13) kHz.

Observation and analysis of the ν2 and ν3 fundamental bands of the H2D+ ion

The high‐resolution absorption spectrum of the D2H+ molecular ion in the 1800–2300 cm−1 region has been measured in a discharge through a mixture of H2 and D2 using a tunable infrared diode laser source and a cooled hollow‐cathode absorption cell. A total of 72 new lines of D2H+ have been observed, as well as five previously measured in ion‐beam experiments by Wing and Shy, and these have been assigned to specific rotational transitions of the ν2 and ν3 fundamental bands. Two different and complementary theoretical models are used to fit these data: one is an A‐reduced asymmetric rotor effective Hamiltonian including the Coriolis and higher‐order rotational interactions between ν2 and ν3; and the other is a supermatrix model in which the matrix of the untransformed Hamiltonian is set up and diagonalized directly, using a large vibration–rotation basis that diagonalizes the vibrational energy. The former approach is less expensive and provides a better fit, but because of the large number of parameters var...

Observation and analysis of the ν2 and ν3 fundamental bands of the D2H+ ion

The high‐resolution absorption spectrum of the D2H+ molecular ion in the 1800–2300 cm−1 region has been measured in a discharge through a mixture of H2 and D2 using a tunable infrared diode laser source and a cooled hollow‐cathode absorption cell. A total of 72 new lines of D2H+ have been observed, as well as five previously measured in ion‐beam experiments by Wing and Shy, and these have been assigned to specific rotational transitions of the ν2 and ν3 fundamental bands. Two different and complementary theoretical models are used to fit these data: one is an A‐reduced asymmetric rotor effective Hamiltonian including the Coriolis and higher‐order rotational interactions between ν2 and ν3; and the other is a supermatrix model in which the matrix of the untransformed Hamiltonian is set up and diagonalized directly, using a large vibration–rotation basis that diagonalizes the vibrational energy. The former approach is less expensive and provides a better fit, but because of the large number of parameters var...

Infrared diode-laser measurements of some atomic helium (4He I 1s nl) fine-structure transitions

Five transitions in neutral atomic helium involving single-electron-excited S, P, and D levels with n = 3 to 8 and Δn = 0 and 2 have been measured in the mid- and far-infrared regions by using tunable-diode-laser sources. The accuracies of the relevant intervals have thus been improved by a factor of approximately 10 with respect to previous optical measurements. These results should be of use in refining the determination of helium energy levels.