Index: trunk/LMDZ.VENUS/libf/phyvenus/photochemistry_venus.F90
===================================================================
--- trunk/LMDZ.VENUS/libf/phyvenus/photochemistry_venus.F90	(revision 4110)
+++ trunk/LMDZ.VENUS/libf/phyvenus/photochemistry_venus.F90	(revision 4111)
@@ -4,7 +4,8 @@
 !
 !     Authors: Franck Lefevre, Francisco Gonzalez-Galindo
+
 !     -------
 !
-!     Version: 14/11/2020
+!     Version: 09/03/2026
 !
 !     ASIS scheme : for details on the method see
@@ -733,20 +734,13 @@
 
 !===========================================================
-!      S4 + hv -> S3 + S
+!      S8 + hv -> S4 + S4
 !===========================================================
 
 nb_phot = nb_phot + 1
 
-indice_phot(nb_phot) = z3spec(1.0, i_s4, 1.0, i_s3, 1., i_s)
-
-!===========================================================
-!      S8 + hv -> S4 + S4
-!===========================================================
-
-nb_phot = nb_phot + 1
-
 indice_phot(nb_phot) = z3spec(1.0, i_s8, 2.0, i_s4, 0., i_dummy)
 
-!Only if ion chemistry included
+! if ion chemistry included
+
 if (ok_ionchem) then
 
Index: trunk/LMDZ.VENUS/libf/phyvenus/photolysis_mod.F90
===================================================================
--- trunk/LMDZ.VENUS/libf/phyvenus/photolysis_mod.F90	(revision 4110)
+++ trunk/LMDZ.VENUS/libf/phyvenus/photolysis_mod.F90	(revision 4111)
@@ -5,5 +5,5 @@
 ! photolysis
 
-  integer, save :: nphot = 34             ! number of photolysis 
+  integer, save :: nphot = 33             ! number of photolysis 
 
 !$OMP THREADPRIVATE(nphot)
@@ -3854,5 +3854,4 @@
 !=  PURPOSE:                                                                 =*
 !=  Read S4 cross-sections                                                   =*
-!=  Billmers and Smith(1991) J. Phys. Chem. ; MPI-Mainz UV/VIS Spectral Atlas=*
 !-----------------------------------------------------------------------------*
 !=  PARAMETERS:                                                              =*
@@ -3887,13 +3886,16 @@
 
 !*** Billmers and Smith(1991) J. Phys. Chem. ; MPI-Mainz UV/VIS Spectral Atlas
-
-      !fil = 'cross_sections/s4_cross_sections_Billmers1991.txt'
+!*** Frandsen (2025) Personal communication
+
+!     fil = 'cross_sections/s4_cross_sections_Billmers1991.txt'
       fil = 'cross_sections/s4_cross_sections_frandsen.txt'
-      print*, 'section efficace S4: ', fil
+
+!     print*, 'section efficace S4: ', fil
 
       if(is_master) then
 
-         !n = 7
-         n = 945
+!     n = 7     ! billmers and smith 1991
+      n = 945   ! frandsen 2025
+
       OPEN(kin,FILE=fil,STATUS='OLD')
       DO i = 1,4
@@ -3911,6 +3913,4 @@
 
       CALL inter2(nw,wl,yg,n,x1,y1,ierr)
-      print*,'S4 cross sections',wl
-!      print*,'S4 cross sections',yg
   
       IF (ierr .NE. 0) THEN
@@ -3919,23 +3919,22 @@
       ENDIF
 
-!      DO iw = 1,nw
-!              if (wl(iw) <= 492.) then
-!                yg1(iw) = 1./3. * yg(iw) !S4 + hv -> S2 + S2
-!                yg2(iw) = 2./3. * yg(iw) !S4 + hv -> S3 + S
-!              else
-!                yg1(iw) = 1.*yg(iw)
-!                yg2(iw) = 0.
-!            end if
-!      enddo     
-
-!     print*,'yg',yg
-!     print*,'yg1',yg1
-!     print*,'yg2',yg2
+!
+!      billmers and smith 1991
+!
+!      do iw = 1,nw
+!         if (wl(iw) <= 492.) then
+!            yg1(iw) = 1./3. * yg(iw) !S4 + hv -> S2 + S2
+!            yg2(iw) = 2./3. * yg(iw) !S4 + hv -> S3 + S
+!         else
+!            yg1(iw) = 1.*yg(iw)
+!            yg2(iw) = 0.
+!         end if
+!      end do     
 
       endif !is_master
 
       call bcast(yg)
-      !call bcast(yg1)
-      !call bcast(yg2)
+!     call bcast(yg1)
+!     call bcast(yg2)
  
       end subroutine rdxss4            
Index: trunk/LMDZ.VENUS/libf/phyvenus/photolysis_online.F
===================================================================
--- trunk/LMDZ.VENUS/libf/phyvenus/photolysis_online.F	(revision 4110)
+++ trunk/LMDZ.VENUS/libf/phyvenus/photolysis_online.F	(revision 4111)
@@ -152,8 +152,8 @@
       j_no         = 28     ! no + hv         -> n + o
       j_n2         = 29     ! n2 + hv         -> n(2d) + n
-      j_h2s        = 30     ! h2s + hv    -> hs + h
-      j_s3         = 31     ! s3 + hv     -> s2 + s
-      j_s4         = 32     ! s4 + hv     -> s2 + s2
-      j_s8         = 33     ! s8 + hv     -> s4 + s4      
+      j_h2s        = 30     ! h2s + hv        -> hs + h
+      j_s3         = 31     ! s3 + hv         -> s2 + s
+      j_s4         = 32     ! s4 + hv         -> s2 + s2
+      j_s8         = 33     ! s8 + hv         -> s4 + s4      
 
 !     j_hdo_od  =           ! hdo + hv        -> od + h