| The infrared absorption spectrum of a molecule provides detailed information about the molecular structure and intramolecular dynamics. Highly-sensitive infrared absorption instruments are often difficult to operate and generally require a large column density (∼1010 molecules/cm 2) which can be difficult to produce for many interesting, highly-reactive species. The work in this thesis concentrates on improving the efficiency and sensitivity of the infrared absorption spectroscopy of molecular ions and applying the new techniques to a number of interesting ionic systems.;An automated color center laser spectrometer, tunable from 2900--4200 cm-1 has been constructed. New diagnostic electronics have also been developed which, when combined with the spectrometer, produce scanning rates that are more than an order of magnitude faster than previous instruments.;Two sensitivity increasing techniques have been developed. The first of these is an auto-balancing subtraction technique for mid-infrared detectors, which improves the efficiency and reliability of double-beam noise subtraction. The other is frequency modulation (FM), a laser based modulation scheme capable of achieving shot-noise limited performance. FM when coupled with ion-velocity modulation has been shown to achieve detection limits as low as 5 x 10-10 cm-1Hz-1/2, an improvement of about an order of magnitude over previous experiments.;These new techniques and instruments have been used to study the kinetics and spectroscopy of the molecular ion H+3 . The experiments include the spectroscopically measured destruction rate of H+3 in a plasma discharge, a survey of H+3 transitions from 3000--4200 cm-1, and a comprehensive evaluation and compilation of H+3 spectroscopy. The results of this work have provided a new tool for studies of problems in theoretical, laboratory, and astronomical spectroscopy.;Finally, a very dense spectrum was recorded of a plasma of CH4, N2, H2, and He using the FM technique. Included in this data are transitions of HCNH+ in highly excited states, and other new species, yet to be identified. |
