The method of laser-induced reaction (LIR) is used to obtain high-resolution IR spectra of CH2D(+) in collision with n-H2 at a nominal temperature of 14 K. For this purpose, a home-built optical parametric oscillator (OPO), tunable in the range of 2500-4000 cm(-1), has been coupled to a 22-pole ion trap apparatus. In total, 112 lines of the ν1 and ν4 bands have been recorded. A line list is inferred from a careful analysis of the shape of the LIR signal. Line positions have been determined to an accuracy of 1 × 10(-4) cm(-1), allowing for the prediction of pure rotational transitions with MHz accuracy. In addition, an IR-THz double-resonance LIR depletion technique is applied to H2D(+) to demonstrate the feasibility for pure rotational spectroscopy with LIR.

We present a continuous-wave optical parametric oscillator (OPO) capable of high resolution spectroscopy at wavelengths between 4.8 μm and 5.4 μm. It is based on periodically poled lithium niobate (PPLN) and is singly resonant for the signal radiation around 1.35 μm. Because of the strong absorption of PPLN at wavelengths longer than 4.5 μm, the OPO threshold rises to the scale of several watts, while it produces idler powers of more than 1 mW and offers continuous tuning over 15 GHz. A supersonic jet spectrometer is used in combination with the OPO to perform measurements of the transient linear molecule Si(2)C(3) at 1968.2 cm(-1). Fifty rovibrational transition frequencies of the ν(3) antisymmetric stretching mode have been determined with an accuracy on the order of 10(-4) cm(-1), and molecular parameters for the ground and the v(3) = 1 state have been determined most precisely.

Context. Deuterated forms of CH + 3 are responsible for deuterium fractionation in warmer environments. Current searches for CH 2 D + are hampered by a lack of accurate laboratory data. Aims. We demonstrate that IR spectroscopy at very high resolution can make accurate rotational predictions. Methods. By combining a low-temperature ion trap with a narrow-bandwidth IR light source, we are able to measure vibrational transitions with high accuracy. A subsequent fit using an asymmetric rotor model allows predictions of MHz accuracy or even better. Results. We predict rotational transitions up to 1.5 THz.