RAMAN SPECTROSCOPY IN THE PRESENCE OF FLUORESCENCE

• US 3,807,862 A
• Filed: 12/18/1972
• Issued: 04/30/1974
• Est. Priority Date: 12/18/1972
• Status: Expired due to Term

• Current Assignee: Douglas Albert Hatzenbuhler
• Original Assignee: Douglas Albert Hatzenbuhler
• Inventors: Hatzenbuhler, Douglas Albert
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): McGraw, V. P.
• Application Number:
  US05/316,347
• Time in Patent Office: 498 Days
• Field of Search: 356/75,114,117
• US Class Current: 356/301
• CPC Class Codes: G01J 3/44 Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry

Abstract

A fluid sample Raman-scatters a plane-polarized laser beam. Sample radiation intensity perpendicular to the laser beam, and perpendicular to its plane of polarization, is compared to sample radiation intensity perpendicular to the laser beam, but in its plane of polarization, in order to provide a measure of Ramanscattering independent of sample fluorescence.

Claims

1. Apparatus for use in Raman spectroscopy, comprising:

first means for providing a sample of freely-reorienting material at a given location O;

second means for directing a substantially monochromatic, planepolarized beam of Raman-scatterable radiation to said sample at said location O for causing said sample to emit radiation in response to said beam and from said location O;

third means for detecting substantially only such component of radiation as comes from said location O, is in response to said beam, and is along the direction of the electric vector of said beam and for detecting substantially only such component of radiation as comes from said location O, is in response to said beam, and is perpendicular to the direction of the said electric vector;

fourth means connected to said third means for producing a signal representative of the difference between the intensity of the first said radiation component and the intensity of the second said radiation component.

2. The apparatus of claim 1, wherein:

said third means includes an element at a location X for picking up said first said radiation component and also an element at a location Z for picking up said second said radiation component;

said second means being at a location -Y;

said locations -Y, Z and X defining with said location O, the directions of said beam, of said first said radiation component, and of said second said radiation component, respectively, said directions being orthogonal and intersecting at said location O.

3. The apparatus of claim 1, wherein, said second means includes polarizing means for varying the plane of polarization of said beam such that sometimes said first said radiation component is directed to a predetermined location, but other times said second said radiation component is instead directed to said predetermined location;

said third means having an element at said predetermined location for picking up both said radiation components.

4. The apparatus of claim 1 wherein said beam, said first said radiation component, said second said radiation component are along the respective orthogonal axes Y, Z, and X, the origin of which axes is at said location O;

said second means being a polarizer operable to polarize said beam so that said electric vector is alternately along said X axis and along said Z-axis, whereby said first said radiation component alternates with said second said radiation component along one of said axes;

said third means being located on said one of said axes for alternately detectinG said first said radiation and said second said radiation components.

5. The apparatus of claim 1, wherein, said fourth means include means for producing a pair of signals respectively representative of the intensity of said first said radiation component and the intensity of said second said radiation component, said fourth means also including means responsive to said pair of signals for producing the first said signal.

6. The apparatus of claim 5, wherein:

said third means includes an element at a location X for picking up said first said radiation component and also an element at a location Z for picking up said second said radiation component;

said second means being at a location -Y;

said locations -Y, Z and X defining with said location O, the directions of said beam, of said first said radiation component, and of said second said radiation component, respectively, said directions being orthogonal and intersecting at said location O.

7. The apparatus of claim 5, wherein, said second means includes polarizing means for varying the plane of polarization of said beam such that sometimes said first said radiation component is directed to a predetermined location, but other times said second said radiation component is instead directed to said predetermined location;

said third means having an element at said predetermined location for picking up both said radiation components.

8. The apparatus of claim 5, wherein said beam, said first said radiation component, and said second said radiation component, are along the respective orthogonal axes Y, Z, and X, the origin of which axes is at said location O;

said second means being a polarizer operable to polarize said beam so that said electric vector is alternately along said X axis and along said Z-axis, whereby said first said radiation component alternates with said second said radiation component along one of said axes;

said third means being located on said one of said axes for alternately detecting said first said and said second said radiation components.

9. A spectroscopic method for analyzing a fluorescing sample, comprising:

the first step of providing said sample in freely-reorienting form;

the second step of providing a beam of monochromatic plane-polarized radiation;

the third step of irradiating said sample with said beam;

the fourth step of detecting radiation emitted by said sample in response to said beam and along the direction of the electric vector of said beam, and while said beam is irradiating said sample;

the fifth step of detecting radiation emitted by said sample in response to said beam and perpendicular to the direction of the said electric vector, and while said beam is irradiating said sample; and

the sixth step of comparing the intensity of such radiation as is detected in said fourth step with the intensity of such radiation as is detected in said fifth step and obtaining the difference between said intensities.

10. The spectroscopic method of claim 9 wherein, said second step includes periodically changing the orientation of said plane of polarization, in such sense and amount, that one of said detecting steps periodically detects the sample-emitted radiation normally detected by the other of said detecting steps.

11. Instrumentation for use in spectroscopy, of the type wherein a sample scatters a plane-polarized beam of monochromatic light incident thereon and wherein the practice is to detect, and to produce signals corresponding to, only such components of light as are emitted from said sample in response to said beam, and correspond to Raman scattering by said sample, are emitted from said sample in directions both perpendicular and parallel to the electric vector of said beam, and wherein there are comparing means for receiving said signals and providing a measure of the difference between the intensities of the parallel components of said light emitted from said sample, and the iNtensities of the perpendicular components thereof;

said instrumentation comprising, in combination, a polarizing means operable for causing said beam to be polarized such that its said electric vector can be oriented in one sense or the other corresponding to one or the other of said directions, said comparing means including a lock-in amplifier for amplifying said signals, said amplifier being adapted to amplify a signal having a given frequency; and

there being means for operating said polarizing means such as to cause the said senses of orientation of said electric vector to alternate at said given frequency.

12. The instrumentation of claim 11, wherein said polarizing means is a Kerr cell.

13. The instrumentation of claim 11, wherein said polarizing means is a Pockels cell.