Method and system for sensitive detection of molecular species in a vacuum by harmonic detection spectroscopy
US5880850A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 16, 1997 |
| Grant date | Mar 9, 1999 |
| Priority date | — |
| Expiry date | Oct 16, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01J3/4338
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Provided is a novel method and system for harmonic detection spectroscopy. The method comprises providing a cell having a sample region which is circumscribed by at least one wall. The cell has at least one light entry/exit port, with each entry/exit port containing a light transmissive window having a surface facing the sample region and disposed so as to seal the cell in the circumferential direction. A sample gas flows through the sample region in a direction parallel to a cell central axis, and the cell operates at less than atmospheric pressure. A frequency and/or amplitude modulated light source is provided for directing a light beam through one of the at least one light transmissive windows into the cell. The light source modulation amplitude is set to a value which approximately maximizes the value of a harmonic signal at the center of the absorption feature due to the detected gas phase molecular species inside the sample region, and the center frequency of the light source is adjusted so that it is either locked to the center of the absorption feature or repetitively scanned over the frequency range which includes the feature. A spectra is then generated which may be reco…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.