A millimeter/submillimeter velocity modulation spectrometer for studies of molecular ions

C. Savage, Lucy M Ziurys

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

A millimeter/submillimeter direct absorption spectrometer has been constructed that employs velocity modulation to selectively detect molecular ions. The instrument consists of a phase-locked Gunn oscillator/Schottky diode multiplier source, a gas absorption cell, and an InSb hot-electron bolometer detector. The gas cell is a single-pass system with two ring-type discharge electrodes at either end, which are connected to an rf power supply. Modulation of the ac discharge at a rate of 50 kHz and phase-sensitive detection at 1f allows for selective observation of molecular ion signals and suppression of absorption from neutral species. The spectrometer can also be used in source-modulated mode, where the signal-to-noise ratio for signals generated in an ac plasma are significantly better than for dc discharges. Combining source modulation with the ac discharge for signal detection and velocity modulation for ion identification provides a powerful technique for molecular ion spectroscopy at millimeter/submillimeter wavelengths. This instrument has been used to measure the pure rotational spectra of C O+, HC O+, and S H+ with better precision than previous studies.

Original languageEnglish (US)
Article number043106
JournalReview of Scientific Instruments
Volume76
Issue number4
DOIs
StatePublished - Apr 2005

Fingerprint

velocity modulation
molecular ions
Spectrometers
Modulation
spectrometers
Ions
modulation
Gunn oscillators
Gas absorption
Bolometers
Hot electrons
signal detection
Signal detection
multipliers
rotational spectra
bolometers
Schottky diodes
cells
hot electrons
gases

ASJC Scopus subject areas

  • Instrumentation
  • Physics and Astronomy (miscellaneous)

Cite this

A millimeter/submillimeter velocity modulation spectrometer for studies of molecular ions. / Savage, C.; Ziurys, Lucy M.

In: Review of Scientific Instruments, Vol. 76, No. 4, 043106, 04.2005.

Research output: Contribution to journalArticle

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