Figure 2. External Reflectance of 0.05 µm SiO2
on Aluminum (p-polarization).
The Seagull™* is a powerful attachment for examining numerous types
of samples using a variety of reflection techniques. This unique accessory
can be easily adapted for external, internal or diffuse reflection spectroscopy.
In addition, it can be operated over a broad range of incident angles without
misaligning the system, without defocusing the incident radiation, and without
changing the polarization of the incident beam. This makes the Seagull™
extremely versatile and flexible. The Seagull™ also incorporates Harrick's
PermaPurge™ feature which permits changing the angle of incidence without
interrupting the purge of the spectrometer.
- Variable angle external and internal reflectance.
- Ideal for examining a wide variety of samples, including powders, optical
coatings, opaque substrates, films on opaque substrates, and slightly curved
- Excellent tool for studying liquids and films on liquids by external reflectance,
for depth profiling, and for determining optical constants.
- Multi-purpose, variable angle reflection attachment.
- Internal, external, and diffuse reflectance capabilities.
- Continuously variable angle of incidence, from 5° to 85°.
- Focuses the incident beam on the sample for all incident angles.
- Always centers the incident beam on the same area of the sample.
- Maintains polarization for angles.
- No realignment of the accessory or repositioning of the sample required
when varying the incident angle.
- High optical throughput.
- PermaPurge™ permits changes in angle without interrupting the purge
of the system.
- Ming-Sung™ ATR Rotator for studying oriented polymers available
- Convenient liquid, powder, and heated sampling accessories available.
angle reflection spectroscopy is becoming increasingly important. Certain samples
such as powders, opaque substances, films on opaque substrates, and films on
liquids are tedious or practically impossible to analyze with conventional transmission
spectroscopic equipment. The analysis of such samples with reflection spectroscopy,
however, is straightforward.
The Seagull™ is shown in Figure 1. Three mirrors (M1, M2, and M3) direct
the beam to an ellipsoid (E1) that focuses the beam onto the sample. The sample
reflects the light onto a second ellipsoid (E2). Ellipsoid E2 reflects the beam
from mirrors M4, M5, and M6 onto the detector of the spectrometer. Mirrors M3
and M4 are coupled to rotate together, in mirror image fashion. This directs
the beam to and from different portions of the ellipsoids, changing the incident
angle of the beam on the sample. This configuration automatically preserves
the optical alignment for any selected angle of incidence.
The Seagull™ is ideal for examining surface and optical coatings, for
measuring optical constants, and for liquid or electrochemical analysis with
the appropriate cells. Sampling accessories are available for convenient sampling
of a variety of types of samples. For ATR studies, the Seagull can be equipped
with our Internal Reflection Kit (SEA-IRK). This kit includes a ZnSe hemispherical
ATR crystal mounted in a holder that slides into the Seagull in place of the
specular reflectance holder. The holder has a built-in pressure applicator.
The kit also includes a compatible pressure plate.
For specular reflectance of liquids, the trough liquid (SEA-TLC) cell provides
an open reservoir to contain the sample. The trough readily mounts onto the
standard specular reflectance holder.
For heated studies, a sample stage (SEA-HOT) is available that can be heated
to 150°C. This stage can be used to support samples for either ATR or specular
For ATR studies of liquids, a flow-through liquid cell (SEA-FLC) is offered.
This cell is equipped with two luer ports and seals against the ATR crystal
with an o-ring. The cell can be used for both flow-through measurements and
for applications requiring a sealed liquid cell. A temperature-controlled version
of the cell (SEA-HLC) is also available for examining liquids from room temperature
For ATR measurements of powders, a convenient powder holder (SEA-PSH) is available.
This holder provides a spring-loaded removable cup that minimizes spillage of
the sample while optimizing contact with the ATR crystal.
For studying oriented polymers and determining ordering in systems with molecules
on inorganic surfaces, our Ming-Sung™ ATR Rotator (MNP-SEA) is available.
This rotator is a specially designed crystal holder that permits a 0° to 90°
rotation of the sample without dismounting the sample. It is compatible with
the hemispheres that can be purchased separately or with the Internal Reflection
In addition, a model of the Seagull™ with independently variable angles
of incidence and collection is available on special order.