Raman App

New: version 2.0 now available!

See what's new in version 2.0.

The Raman application is used by scientists doing Raman Spectroscopy to convert between various units like wavenumber, nanometers, gigahertz or electron volts.

You set the excitation wavelength and the signal wavelength in nanometers and Raman gives you the Raman shift expressed in wavenumber ( cm-1), GHz and meV. Or you can enter a Raman shift and get the signal wavelength for the given excitation. These are just a few examples. You can change any of the values and the rest updates.

You’ll find a little background on what Raman Spectroscopy is below, as well as a link to the App Store.

Raman is localized for both English and French. If you'd like to help me translate it in your language, please contact me!

If you need help or have an issue please use the contact form.

Stacks Image 500

Spectroscopy tab

The spectroscopy tab is for calculating the Raman shift between the excitation laser and the signal.

You can edit any of the values listed and the others will be updated in the following manner:

  • Changing the Excitation Wavelength will compute the Raman Shift (all three units) with the current Signal Wavelength.
  • Changing the Signal Wavelength will compute the Raman Shift (all three units) with the current Excitation Wavelength.
  • Changing any of the Raman Shift units will compute the Signal Wavelength with the current Excitation Wavelength and update the other units.

Positive Raman shift values are for Stokes shifts, while negative values represent Anti-Stokes shifts.

Bandwidth tab

The bandwidth tab is for calculating the bandwidth at an arbitrary wavelength.

This is used to determine the required resolution of the detection to discriminate between the excitation and a signal peak for instance.

For example, a bandwidth of 2 nm is equivalent of 70.4 cm-1 at 532 nm, but the same bandwidth of 2 nm would be 32.37 cm-1 at 785 nm.

First set the reference wavelength, then enter the bandwidth in the known unit and read the other unit values.

Ready for iOS11 and iPhone X

Version 2.0 takes advantage of the newest technologies in iOS 11 and adapts to any iOS device, including the new iPhone X and iPads. It still supports iOS 9 and above.

New light/dark mode

A totally redesigned interface with both a dark and a light-themed mode. For example, you could choose a dark mode when in the lab and the light mode when in your office.

Light theme

  • Spectroscopy

    Stacks Image 453
  • Bandwidth

    Stacks Image 455
  • Edit parameters

    Stacks Image 457

Dark theme

  • Spectroscopy

    Stacks Image 962
  • Bandwidth

    Stacks Image 967
  • Edit parameters

    Stacks Image 972

Redesigned data entry

Custom interface for easier data entry. Just what you need at your fingertips. Contextual help tells you what will happen. Do simple arithmetic right in the data entry panel.

Stacks Image 957
Stacks Image 1015

Unlock convenient memories to save parameters

With an in-app purchase, unlock up to 10 saved values for each parameter and recall them quickly. Instead of retyping the same parameters (excitation wavelengths, wavenumbers, etc.), easily select saved parameters from a list or swipe through them without even going into the edit mode[1].

1: swipe to cycle through memories is available on iOS 11 and above only.

Stacks Image 994

See the swipe through memories in action

With the in-app purchase unlocked and iOS 11 and above, you can easily swipe through saved parameters by swiping left or right on a parameter. Swiping from left to right cycles downwards through memories and swiping from right to left cycles upwards. Tap the image below to see it in action.

Swiping only cycles through saved parameters, skips unused memories, and loops around.

Purchase the memories function

To unlock the memories function use the in-app purchase button in the about page.

This will unlock the memories function keys in the data entry panel and enable the swipe gesture on iOS11+. It will also give access to any special features included in future versions for free.

What is Raman Spectroscopy?

“A fingerprint by which molecules can be identified”

Raman spectroscopy is a technique which relies on inelastic scattering, also called Raman scattering. The excitation laser interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down (see the Stoke and Anti-Stokes sidebar). This shift in energy gives information about the vibrational modes in the system and is called the Raman shift.

Raman shifts are typically reported in wavenumbers, which are units of inverse length, as this value is directly related to energy. In order to convert between spectral wavelength and wavenumbers of shift in the Raman spectrum, the following formula can be used:

$$\Delta \omega = { \frac{1}{\lambda_0} - \frac{1} {\lambda_1} } $$

where \(\Delta \omega\) is the Raman shift expressed in wavenumber, \(\lambda_0\) is the excitation wavelength, and \(\lambda_1\) is the signal wavelength.

Most commonly, the unit chosen for expressing wavenumber in Raman spectra is the inverse centimeters (cm-1) and wavelength is often expressed in units of nanometers (nm).

While it's easy to think in terms of wavelengths or frequencies, it's harder to compute Raman shifts in wavenumbers (cm-1) in our head. This is what the Raman app does: it helps researchers convert the various units used in Raman spectroscopy. For example, convert a Raman shift expressed in cm-1 into signal wavelengths expressed in nm with this formula:

$$\lambda_1 = \frac{1} {\frac{1} {\lambda_0} - 10^{-7} \Delta \omega} $$

  • Stokes and Anti-Stokes

    If the final vibrational state of the molecule is more energetic than the initial state, the inelastically scattered photon will be shifted to a lower frequency for the total energy of the system to remain balanced. This shift in frequency is designated as a Stokes shift. If the final vibrational state is less energetic than the initial state, then the inelastically scattered photon will be shifted to a higher frequency, and this is designated as an anti-Stokes shift. See the energy diagram below.

  • Stacks Image 438