Spectrum File Formats

This page answers one question: will TFStudio read the file my instrument writes? For almost every UV/Vis/NIR spectrophotometer the answer is yes, because the importer reads the shapes real instruments produce rather than one tidy ideal. Import happens in the Measured Spectra window.

Delimited text

Any λ, value table, whatever the extension: .csv, .txt, .asc, .dat, .dpt, .ttt, and the rest.

Detected automatically	Values it handles
Delimiter	Comma, semicolon, tab, or runs of spaces
Decimal separator	Point or comma. 400,5;88,51 reads correctly
Wavelength unit	Nanometres, micrometres, or wavenumber in cm⁻¹
Quantity	Transmittance, reflectance, absorptance
Y scale	Fraction, percentage, or absorbance

Everything detected can be overridden before you add the curve, so a file that declares nothing still imports in two clicks.

Headers

Instruments rarely put one clean row of column names above the numbers. These layouts are read as intended:

• A settings block before the data. Header lines that look like numbers, as PerkinElmer writes them, do not become part of the spectrum.
• A marker line. #DATA, >>>>>Begin Spectral Data<<<<< and similar say where the header ends, and the data is taken from after it.
• Names on one line, units on the next. Wave ; Sample ; Reflectance above [nm] ; [counts] ; [%] names each column and reads each column’s own unit, so a percentage in one column does not set the scale of its neighbours. Units written bare, nm deg deg, are read the same way.
• A commented-out header. A leading ;, # or // is a marker, not a column, whether it stands on its own or is written against the first name, as in #ROIidx.
• The wavelength column need not be first. A column named Wavelength or Lambda is the axis wherever it sits.
• Quoted names. "Wavelength nm.","R%" imports as reflectance.
• Either spelling of a percentage. %T and T% both mean transmittance.

Rows

• A label at the start of every row, as reflectometers often write, is recognised and dropped: uR 402.5238 0.0 0.237728 0.01 is one data row.
• Rows with no value are left out and counted, so a file that alternates a reading with a blank line tells you how many rows it lost rather than silently halving the measurement.
• Descending wavelengths are sorted on the way in.
• A trailing statistics block after the data is ignored.

Several samples in one file

Software that measures a batch writes one wavelength column per sample:

AR_front,,AR_back,
Wavelength (nm),%T,Wavelength (nm),%T
400.00,88.51,400.00,87.90

The repeated wavelength columns are recognised as sample boundaries rather than offered as curves, and each measurement is named after the sample it belongs to. Import one column with Add to design, or all of them with Add all curves.

JCAMP-DX

The IUPAC spectroscopy standard, .dx and .jdx, read and written. It carries its own units and quantity, so it imports without configuration. Compound LINK files import every block as a separate curve. Both the fixed-format XYDATA compressions and the XYPOINTS pair list are supported.

Export writes JCAMP-DX in the same wavelength unit and Y scale you choose for CSV, which makes a TFStudio curve loadable in any spectroscopy package.

Ellipsometry files

A Ψ and Δ pair is imported in Measured Ellipsometry, not in Measured Spectra, and everything above about delimiters, decimal separators and headers applies to it. A few things are specific to these files.

The X axis may be photon energy. Ellipsometry software often works in eV. An axis is read as eV only when the header says so, never from the numbers: an eV axis and a micrometre axis span the same range, so a guess would convert silently and be invisible afterwards.

Which column is Ψ and which is Δ is decided from the values rather than the order, because vendors disagree about the order. Ψ is the arctangent of a magnitude ratio and cannot leave 0 to 90 degrees, so a column that goes above 90 or below zero is Δ. Either can be overridden in one click.

The angle of incidence is read from a header line that names it (AOI 70, Angle of incidence 70), from a data column named the same way, from a column heading that lists the angles, as Psi (45.00, 50.00°) does, or from a column’s own name where it is written @55°. A file that repeats its wavelengths once per angle is split into one Ψ/Δ pair per angle. A measurement at several angles has no single angle for its header to state, so each curve carries its own in its name and an export of those curves reads back with every angle intact. A file that states its angle in none of those places imports at the angle set in the panel, so check it.

Several regions of interest in one file, as an imaging ellipsometer writes them under a ROIidx column, are split the same way: one Ψ/Δ pair per region, named after it.

Δ in any range. Software may write Δ between -180 and 180, or -90 and 270. It is the same angle, and it is drawn and fitted on the 0 to 360 axis as such. A curve that steps off the end of its own range is read as carrying on round the circle, so nothing is interpolated through the middle of the turn, and a residual against the design is always taken the short way round.

What has been checked

Instrument and layout	Result
SENTECH SpectraRay. ; WAVELENGTH <angle> <angle> header, then λ, Ψ, Δ	Imports. Columns typed from the values. The angle appears only as a column heading, so set it in the panel.
ADAP. SE PSI DELTA header with a separate AOI line	Imports, angle read from the header. This exporter writes tan Ψ and cos Δ under headings that say PSI and DELTA; the Δ column is detected and the window says so. Convert to degrees before fitting.
J.A. Woollam WVASE, spectroscopic. Unit line, then λ, angle, Ψ, Δ	λ, Ψ and Δ import. In this export the angle column carries no name, so it is offered as a curve instead of splitting the file by angle: set the angle by hand, or name that column AOI first.
J.A. Woollam WVASE, single wavelength. Angle of Incidence, Psi, Delta	Not read. This is an angle sweep at one wavelength; the window’s curves are functions of wavelength.
J.A. Woollam CompleteEASE, variable angle. Wavelength (nm) Psi (45.00, 50.00, … °) Delta (45.00, 50.00, … °) over one Ψ, Δ column pair per angle	Imports as one Ψ/Δ pair per angle, each named and angled from the heading. Δ is written between -90 and 270 and lands on the 0 to 360 axis.
Accurion, Park Systems EP4Control. #ROIidx Lambda Bandwidth AOI … Delta Psi with a # unit row, one row per region of interest per wavelength	Imports. The wavelength is found by name in the third column, Δ before Ψ is read by name, the angle comes from its column, and each region of interest becomes its own Ψ/Δ pair.

Any other delimited file holding a wavelength, a Ψ and a Δ should import: those are what could be obtained to check against, not the limit of what works. A file that does not import is worth reporting with the file attached.

A file being readable is not the same as its measurement being one TFStudio models. Reflection ellipsometry on an isotropic sample is what these curves mean, and transmission ellipsometry, Mueller-matrix data, and an instrument’s native Is/Ic/Ic′ are not read at all: see what kind of measurement the window takes.

Instruments this has been checked against

Real exports from these have been read end to end: PerkinElmer (both the PEDS ASCII format and JCAMP-DX), Shimadzu UV-Probe, Agilent Cary, Filmetrics, Avantes AvaSoft, Ocean Optics, and reflectometer and ellipsometer text formats.

If yours is not on the list it will very probably still import, because the list is instruments that were tested rather than instruments that work. A file that does not import, or imports as the wrong quantity, is worth reporting with the file attached.

What it does not read

• Binary instrument files. PerkinElmer .sp, Cary .BSW, Galactic .SPC, Bruker OPUS, and the Avantes .TRM and .ROH families. Every one of these has an ASCII or JCAMP-DX export in its own software; use that.
• Detector counts. A column of raw counts imports as a spectrum and is scaled as though it were a percentage. Pick the column your instrument reports as R or T, not the raw signal, dark, or reference columns.