Mid-infrared spectrometer Scanning SFG

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The Scanning SFG Spectrometer is a picosecond scanning sum frequency generation (SFG) vibrational spectrometer designed for in-situ investigation of surfaces and interfaces. It utilizes a narrowband mid-IR pulse whose wavelength is changed point-by-point during measurement, with the SFG signal recorded by a time-gated photomultiplier for high sensitivity and selectivity.

Advantages

• Sensitive and selective to the orientation of molecules in the surface layer
• Intrinsically surface specific
• Selective to adsorbed species
• Sensitive to submonolayer of molecules
• Applicable to all interfaces accessible to light
• Nondestructive
• Capable of high spectral and spatial resolution

Applications

• Investigation of surfaces and interfaces of solids, liquids, polymers, biological membranes, and other systems
• Studies of surface structure, chemical composition, and molecular orientation
• Remote sensing in hostile environments
• Investigation of surface reactions under real atmosphere, catalysis, surface dynamics
• Studies of epitaxial growth, electrochemistry, material and environmental problems

Sum Frequency Generation Vibrational Spectroscopy

• SFG-VS is a powerful and versatile method for in-situ investigation of surfaces and interfaces
• Combines a pulsed tunable IR laser beam with a visible beam to produce an output at the sum frequency
• Highly surface specific due to symmetry breaking at interfaces
• Provides spectral information on surface vibrational transitions
• Enables extraction of detailed information on ordering and orientation of molecular groups at the interface

System Features and Design

• Picosecond mode-locked Nd:YAG laser and optical parametric generator in one unit
• Spectroscopy module with PMT-based signal detectors, data acquisition system, and dedicated LabView® software
• Fast wavelength scan (sweep) for rapid access to a wide spectral range
• Broad spectral region: automatically tuned from 625 to 4300 cm⁻¹
• High spectral resolution (3 cm⁻¹)
• Easily controlled adjustment of polarization optics
• Two-unit design: laser light source PT501 and spectroscopy module
• Temporal gate in detection system reduces noise and allows operation in illuminated rooms
• Adjustable IR beam spot size to avoid sample damage
• Motorized polarization switch for IR (standard), VIS and SFG (optional)
• Continuous energy monitoring for normalization of SFG spectra
• Large, customizable sample compartment for various extensions (e.g., Langmuir-Blodgett trough, temperature/humidity control)
• All high energy pulsed beams are enclosed for safety; sample area has a special cover

Modifications and Options

• Double resonance SFG spectrometer: allows investigation of vibrational mode coupling to electron states at a surface
• Phase sensitive SFG spectrometer: allows measurement of the complex spectra of surface nonlinear response coefficients
• Single or double wavelength VIS beam: 532 nm and/or 1064 nm
• One or two detection channels: main signal and reference
• Second harmonic generation surface spectroscopy option
• Motorized polarization control for VIS and SFG beams
• Larger sample compartment to accommodate Langmuir trough
• Simultaneous measurement of s and p polarization of SFG signal

Polarization Control

• Simultaneous measurement of S and P polarization in dual detection system
• Motorized polarization control for SFG, VIS, and IR beams
• Automatic change of polarization and energy attenuation for measurements without opening the spectrometer

Accessories

• Six axis sample holder
• Sealed temperature controlled sample chamber
• Larger sample area for Langmuir trough
• Motorization of polarization control for VIS and IR beams, polarization analyzer for SFG signal

Characteristics / Technical Specifications

• Spectral range: 625 – 4300 cm⁻¹ (Classic and Double resonance, VIS 532 nm); 1000 – 4300 cm⁻¹ (VIS 420–680 nm and Phase sensitive)
• Spectral resolution: < 3 cm⁻¹
• Spectra acquisition method: Scanning and fast wavelength sweep
• Sample illumination geometry: Top side, reflection
• Incidence beams geometry: Co-propagating, non-colinear
• Incidence angles: Fixed, VIS ~60°, IR ~55° (optional: tunable)
• VIS beam wavelength: 532 nm (Classic and Phase sensitive); 532 nm and tunable 420–680 nm (Double resonance)
• Polarization (VIS, IR, SFG): Linear, selectable “s” or “p”, purity > 1:100
• IR Beam spot on the sample: Adjustable, ~200–600 µm (Classic and Double resonance); Fixed (Phase sensitive)
• Sensitivity: Air-water interface spectra (Classic and Double resonance); Solid sample spectra (Phase sensitive)
• Laser light source model: PT501-SH
• Pulse duration: 29 ± 5 ps
• Pulse repetition rate: 100 Hz
• UV-VIS source for Double resonance SFG: PT401
• Physical characteristics (footprint): 1300 × 1200 mm (Classic), 1800 × 1200 mm (Double resonance), 1400 × 1200 mm (Phase sensitive)