Hannover 2013 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

MO: Fachverband Molekülphysik

MO 11: Infrared and Microwave Spectroscopy

MO 11.1: Vortrag

Dienstag, 19. März 2013, 11:00–11:15, F 107

Fast acquisition of high-resolution microwave spectra with broadband FT-MW spectroscopy — •Dennis Wachsmuth, David A. Dewald, Michaela K. Jahn, and Jens-Uwe Grabow — Institut für Physikalische Chemie, Gottfried Wilhelm Leibniz Universität Hannover, Germany

The need for quite precise predictions of molecular geometries and potential energy barriers to internal motions necessary to calculate rotational transition frequencies is a major obstacle in narrowband highresolution microwave spectroscopy techniques. We present the recently developed in-phase/quadrature-phase modulation passage-acquiredcoherence technique (IMPACT) Fourier-Transform spectrometer as a new experimental tool for high-resolution broadband measurements of rotational spectra, here implemented in the 2.0-26.5 GHz frequency range. This method combines the advantages of broadband spectrometers with the resolution of cavity based narrowband instruments and therefore accelerates the precise acquisition of wide spectral ranges. Since the design is based on the upconversion of a chirp in the -500 to +500 MHz base band from an arbitrary waveform generator to the desired signal band at microwave frequencies in one step, no disadvantageous frequency multiplication, filtering or difference frequency generation is necessary. After excitation of the supersonic jet-expansion comprising the molecular ensemble, the molecular response signal is downconverted and detected in the DC-centered base band, again in a single step. The obtained spectrum exhibits a linewidth of <5 kHz (HWHM), the signal frequency determination accuracy is <1 kHz.