High-resolution rovibrational and rotational spectroscopy of the singly deuterated cyclopropenyl cation, c-CHD.

Applying a novel action spectroscopic technique in a 4 K cryogenic ion-trap instrument, the molecule c-CHD has been investigated by high-resolution rovibrational and pure rotational spectroscopy for the first time. In total, 126 rovibrational transitions within the fundamental band of the symmetric C-H stretch were measured with a band origin centred at 3168.565 cm, which were used to predict pure rotational transition frequencies in the ground vibrational state.

Rovibrational spectroscopy of the CH-He and CH-He complexes.

A cryogenic 22-pole ion trap apparatus is used in combination with a table-top pulsed IR source to probe weakly bound CH-He and CH-He complexes by predissociation spectroscopy at 4 K. The infrared photodissociation spectra of the C-H stretching vibrations are recorded in the range of 2720-2800 cm. The spectrum of CH-He exhibits perpendicular transitions of a near prolate top with a band origin at 2745.

High-resolution infrared action spectroscopy of the fundamental vibrational band of CN.

Rotational-vibrational transitions of the fundamental vibrational modes of the CN and CN cations have been observed for the first time using a cryogenic ion trap apparatus with an action spectroscopy scheme. The lines (3) to (3) of CN and (1) to (3) of CN have been measured, limited by the trap temperature of approximately 4 K and the restricted tuning range of the infrared laser. Spectroscopic parameters are presented for both isotopologues, with band origins at 2000.

Accurate Rotational Rest Frequencies for Ammonium Ion Isotopologues.

We report rest frequencies for rotational transitions of the deuterated ammonium isotopologues NHD, and , measured in a cryogenic ion trap machine. For the symmetric tops NHD and one and three transitions are detected, respectively, and five transitions are detected for the asymmetric top . While the lowest frequency transition of NHD was already known in the laboratory and space, this work enables the future radio astronomical detection of the two other isotopologues.

First Laboratory Detection of Vibration-Rotation Transitions of CH and CH and Improved Measurement of their Rotational Transition Frequencies.

The long-searched C-H stretches of the fundamental ions CH and CH have been observed for the first time in the laboratory. For this, the state-dependent attachment of He atoms to these ions at cryogenic temperatures has been exploited to obtain high-resolution rovibrational data. In addition, the lowest rotational transitions of CH, CH and CD have been revisited and their rest frequency values improved substantially.

Accurate Frequency Determination of Vibration-Rotation and Rotational Transitions of SiH.

The fundamental SiH ion has been characterized in a collaborative work, utilizing a hollow-cathode-discharge laser-spectrometer and a cryogenic ion trap spectrometer. Twenty-three vibration-rotation transitions around 4.75 m have been detected with high accuracy.

Ion kinetics in Ar/H cold plasmas: the relevance of ArH.

The recent discovery of ArH in the interstellar medium has awakened the interest in the chemistry of this ion. In this work, the ion-molecule kinetics of cold plasmas of Ar/H is investigated in glow discharges spanning the whole range of [H]/([H]+[Ar]) proportions for two pressures, 1.5 and 8 Pa.

Sensitivity enhancement in high resolution stimulated Raman spectroscopy of gases with hollow-core photonic crystal fibers.

We show the first experimental evidence of the sensitivity enhancement that can be achieved in high resolution stimulated Raman spectroscopy of gases using hollow-core photonic crystal fibers (HCPCFs). Using low power cw lasers and a HCPCF containing the gas, we have observed more than four orders of magnitude enhancement of sensitivity when compared with the cw single focus regime, and a similar sensitivity to that achieved in the more sensitive quasi-cw setups with multipass cells.

Direct determination of state-to-state rotational energy transfer rate constants via a Raman-Raman double resonance technique: ortho-acetylene in v(2)=1 at 155 K.

A new technique for the direct determination of state-to-state rotational energy transfer rate constants in the gas phase is presented. It is based on two sequential stimulated Raman processes: the first one prepares the sample in a single rotational state of an excited vibrational level, and the second one, using the high resolution quasi-continuous stimulated Raman-loss technique, monitors the transfer of population to other rotational states of the same vibrational level as a function of the delay between the pump and the probe stages. The technique is applied to the odd-J rotational states of v(2)=1 acetylene at 155 K.