Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: To focus-match or not to focus-match inverse spatially offset Raman
  spectroscopy: a question of light penetration   The ability to identify the contents of a sealed container, without the need
to extract a sample, is desirable in applications ranging from forensics to
product quality control. One technique suited to this is inverse spatially
offset Raman spectroscopy (ISORS) which illuminates a sample of interest with
an annular beam of light and collects Raman scattering from the centre of the
ring, thereby retrieving the chemical signature of the contents while
suppressing signal from the container. Here we explore in detail the relative
benefits of a recently developed variant of ISORS, called focus-matched ISORS.
In this variant, the Fourier relationship between the annular beam and a
tightly focused Bessel beam is exploited to focus the excitation light inside
the sample and to match the focal point of excitation and collection optics to
increase the signal from the contents without out compromising the suppression
of the container signal. Using a flexible experimental setup which can realise
both traditional and focus-matched ISORS, and Monte-Carlo simulations, we
elucidate the relative advantages of the two techniques for a range of optical
properties of sample and container.

28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg