A new single grating spectrograph for ultraviolet Raman scattering studies

Abstract

A state-of-the-art single grating spectrograph for Raman scattering studies within the deep ultraviolet (DUV) region of the electromagnetic spectrum is discussed. It is based on a high throughput DUV version of a single-stage monochromator originally designed for use in the visible spectral region. Its key components are two identical, newly designed calcium fluoride camera lenses each consisting of five different individual optical elements. The first of these lenses collimates the Raman scattered DUV radiation entering the spectrometer through its entrance slit. The second lens focuses the collimated beam of dispersed Raman scattered DUV radiation emerging from a high-resolution reflection grating onto a charge coupled device (CCD) detector with enhanced DUV sensitivity. A novel high transmission edge filter is used as a blocking device for a sufficient rejection of the Rayleigh line generating a relatively sharp transmittance cutoff at a Stokes Raman wavenumber shift of about ∼450 cm −1 employing 257 nm DUV excitation. Overall, this new spectrograph enables rapid collection of Stokes DUV Raman scattered photons at f /2 wide apertures with sufficiently large signal-to-noise ratios (SNRs) in relatively short acquisition times and with an effective spectral resolution of approximately ∼6 cm −1 . Backscattered Raman spectra of the following chemicals are presented as typical results illustrating the excellent performance characteristics of this new DUV spectrograph for a variety of experimental conditions within different scattering scenarios and for a relatively wide range of commonly used sample preparation techniques: neat cyclohexane, laboratory air, polycrystalline D-glucose, single crystal L-alanine and a dilute aqueous solution of 2 -deoxyadenosine.

Concentration‐Dependent Hydrogen‐Bonding Effects on the Dimethyl Sulfoxide Vibrational Structure in the Presence of Water, Methanol, and Ethanol

“…Raman Spectroscopy: The experimental Raman setup consisted of a continuous-wave grating-stabilized diode laser operating at 785 nm. The laser beam was focused into the cuvette with the sample under investigation and the backscattered light was collected in a "hole in a mirror" arrangement [56] by an achromatic lens. The signal was spectrally filtered by two long-pass filters (cutoff wavelengths 785 and 800 nm) to suppress elastically scattered light and focused into a fiber-coupled spectrometer.…”

Recent Advances in linear and nonlinear Raman spectroscopy I

“…As an example, a new single grating spectrograph with an f/2 wide aperture and an effective spectral resolution of 6 cm 1 for deep ultraviolet Raman scattering studies was reported by Hecht et al 292 Special calcium fluoride lenses and a novel transmission edge filter were incorporated in this apparatus. Nevertheless, some additional, special advanced Raman instrumentations were reported recently.…”

8.26 Spectroscopic Analysis: Raman Optical Activity

“…For this purpose, Hecht et al 68 have constructed a high quality single grating spectrograph using the 257 nm line of the frequency-doubled argon ion laser for excitation. Though this spectrometer was built with ROA studies for biochemical applications in mind, those spectra have not been published yet.…”