The Anti-Stokes thread (visible fluorescence triggered by infrared)

There are many notes that have anti-Stokes fluorescence, for example all of the Abkhazia notes from 2018 onwards. I have a rudimentary setup to check my notes, using three LED bulbs that have an output at 980nm. That is invisible infrared. The problem is, these three bulbs must all be aimed at the same place on the note which gives me a small area of coverage, only 4cm x 4cm. So I have to “scan” the note under the bulbs.

I'm going to post notes which I think are questionable. These are notes where only one example in my collection has anti-Stokes fluorescence and it does not make sense to me.

2000 Kwacha - Malawi – Numista 

I have a 2016 note, Prefix AA.

On the reverse just below the lower 2000 there is anti-Stokes fluorescence in green. 

2000 Riels - Cambodia – Numista  (P#59a)

I have five of these notes and one of them fluoresces, serial number ង៧2267131. On the reverse, the 2000 denomination that also fluoresces under UV.

10 Dollars (polymer) - Hong Kong – Numista

I have four of these, P#401a to P#401d. The P#401a has an indistinct dull fluorescence which does not seem intentional to me. 

At some point if someone gets a better way to image these notes under IR at 980nm, I would appreciate it if they can be checked and tell us here if they do fluoresce. 

A small update: I got two other P#401a Hong Kong 10 Dollar notes and they have the same indistinct fluorescence under IR. It is like a milky swirl.

So I think there is something going on with those.

Then I found another weird situation, similar to the Cambodia 2000 Riels.

This time it was another Hong Kong note, the paper 20 Dollar note produced in 2014 by Standard Chartered Bank. I have four of these:

20 Dollars (Standard Chartered Bank) - Hong Kong – Numista

I have (so far) the 2010, the 2012 and two of the 2014 notes. On one of the 2014 notes there is obvious, intentional, very strong anti-Stokes fluorescence. That one has a prefix of ED. The one that doesn't have the anti-Stokes fluorescence has a prefix of CR.

That is very interesting!

20 Kwacha (Blind mark at center right) - Malawi – Numista 

I confirmed this one today: only the 2017 version (no other year) has anti-Stokes fluorescence on the obverse, in the same distribution as the rectangle with the 20 visible under UV.

I need to update Numista on this one because these notes also have UVA vs UVC differences (green vs yellow colour)

Couls you post images of the notes you are mentioning (edit them into the posts above).

The only one I can post is the Malawi 20 Kwacha. That's because Foster and Freeman kindly imaged that note for me. At some point I would like to image all my notes, but yesterday was a brief opportunity just to see a variety of imaging techniques that their VSC9000 can do.

Anyway here is the Malawi 20 Kwacha (2017):

That vertical rectangle that is glowing green is an image produced when the note was lit by infrared light at 980nm (invisible to the human eye).

The ink that was excited by the infrared then fluoresces in the visible spectrum.

I'm not convinced this was an intentional security feature but I can tell you it is on all the 2017 notes in my collection.

Here's another one, with spectacular anti-Stokes fluorescence. It is a composite stitched image I have made, using two source photographs taken by the Foster and Freeman forensic company yesterday:

De La Rue Giori - Leonardo da Vinci (prototype/demonstration note) - United Kingdom – Numista

Here is another one kindly provided by the Foster and Freeman forensic company. It involves this Ukraine note:

50 Hryven ("Unity Saves the World") - Ukraine – Numista

I am going to update that entry because I got better infrared images from Foster and Freeman also.

That note has anti-Stokes fluorescence, a very intense green:

That's the same map of Ukraine that fluoresces under UV on the reverse. But this fluorescence was triggered by infrared, not UV. That ink therefore has two components: UV reactive and infrared reactive.

That's a nice effect on the note - interesting that it is active in both IR and UV.

This is my basic home setup of three LED lights at 980nm. With the lights switched on and with a basic phone camera you can still see the infrared spot on the black card. That's where the beams converge:

To get rid of the infrared I tape a Hoya IR cut filter to my phone. Now it looks like this, you cannot tell that the lights are on:

If the anti-Stokes fluorescence is bright and limited in its area, I can get a useable photograph. Here's a 10 Patacas note from Macau (Banco Da China):

This image shows where that anti-Stokes fluorescence is:

The anti-Stokes pattern and position of it differs on the Ultramarino notes. But all the notes in the Zodiac series have it, from both banks.

Here's another one, a 2000 Pesetas note from Spain, year 1992 (issued 1996):

2000 Pesetas (with security line) - Spain – Numista

The anti-Stokes fluorescence is strong and detectable on both sides of the note, but stronger on the reverse:

Here's where that square is on the note:

I have both versions of the 1000 Pesetas note and they fluoresce also.

1000 Pesetas - Spain – Numista

I have a little article here, thanks to the help of the Foster and Freeman forensic company:

Banknotes and their not-so-obvious features. Part 6: anti-Stokes fluorescence | LinkedIn

I found another guy (or he found me on LinkedIN) who has been looking at anti-Stokes fluorescence also. I see Vlad recently joined the forum, here is his thread on Bonistika with very nice photos:

https://bonistika.net/forum/viewtopic.php?t=44972

Hi Brandon, I was very pleased to discover that I'm not the only one interested in spectral images of banknotes and anti-Stokes luminescence.

I'd like to share some of my anti-Stokes photos here; the most beautiful (in my opinion) are banknotes from Thailand and England.

Those are really beautiful, I am amazed you can get those images with a home setup!

I was not aware of any England pounds with this effect, I have now had to order those (of course!)

@bumagomarazzi

Very nice indeed.

What set-up did you use to obtain the images?

My setup:
- dark room,
- camera with manual focus and shutter speed control (I have a Canon 550D),
- IR-cut filter for the lens, as the powerful IR from the laser overexposes unwanted areas,
- 980nm laser anti-Stokes detector,
- and lots and lots of patience.

I focus my camera on the banknote, turn off the lights, open the shutter for 2-5-10 minutes (I find the right time for each individual case experimentally), and sweep the laser beam across the illuminated areas of the banknote. This requires a lot of patience, as a single banknote can take an entire evening.

For eye protection, I wear IR-cutting glasses.

I found a detailed spectrometric measurement of anti-Stokes fluorescence for 50 rubles 1997/2004 - https://www.mikroskopie-forum.de/index.php?topic=40884.0 

Among other things, user said that anti-Stokes phosphors were patented in 1974 - no source is given, but at least we can use that date as a reference in our research.

That would fit with what I found, the first ones definitely known is 1979 Spain notes. And it wasn't present on the 1971 notes.

Just one note I have to check then is the 1976 Spain 5000 Pesetas. But it is pricey! 

bumagomarazzi

My setup:

Very nicely done there.

Well, I received the first part of my new banknotes with anti-Stokes fluorescenсe. Bran, thank you for sharing your findings list!

Spain: 200 pesetas 1980, 500 pesetas 1979, 1000 pesetas 1979. Anti-Stokes.

Those are nice!

I can't wait to see what designs and colours are on the Syria notes. I suspect those will be more arty.

The 2025 Syrian banknotes delighted us with their varied shades of red on the anti-Stokes marks. The different shades have varying luminescence intensities, with the 10 and 50 pound notes being particularly vibrant. Compared to these, the 25 pound note is three to four times weaker (subjectively). The denomination section of the 50 pound note also glows, which, for unknown reason, is absent from the other notes.

Thailand 50 baht ND (2025) polymer

That is a great photo also, I love that!

I recently got another Goznak test note, this one: the Sergei Korolev test note:

Goznak - 100th Anniversary of the birth of Sergei Korolev - Russian Federation (1991-date) – Numista

This one has four different colours of anti-Stokes ink: dark green, bright yellow-green, blue and red.

I cannot photograph it, but this one will look spectacular once it gets photographed properly.

This is a graphic depiction of where some of the anti-Stokes features are:

Another one where I can detect the anti-Stokes but not photograph it, is the Nature 2022 set of four notes by Goznak:

Goznak - Nature 2022 - Russian Federation (1991-date) – Numista

I would be very interested in examining and photographing the anti-Stokes marks on these Goznak notes.

When I buy them, I will definitely share the photos.

Two other notes where I can detect but not photograph the anti-Stokes fluorescence. 

First is the Gibraltar commemorative note, 10 Shillings from 2018:

50 Pence / 10 Shillings (World Tourism Year) - Gibraltar – Numista

Second is a Goznak test note, the 200th Anniversary of Goznak, also from 2018:

Goznak - 200th Anniversary of Goznak - Russian Federation (1991-date) – Numista

In both cases it is a wide distribution of green dots on one side only. I cannot make out what the pattern is (if any). I have multiples of each note, and the appearances are the same.

Another one found, the Goznak Panda note:

Panda - Russian Federation (1991-date) – Numista

That one is quite nice because it has phosphorescent designs also. I cannot photograph the anti-Stokes though.