Theoretical analysis of S1-state lifetime measurements of dyes with picosecond laser pulses

Accumulation of DODCI P isomers by laser excitation

“…In our experiments the S r level populations remain negligibly small because the excitation intensities / L are small compared to the saturation intensities /N,S =A"L/^N(^L)^N and / P , s -hp L /ap(X L )r P of ground-state absorption bleaching which are in the MW/cm 2 region (A is the Planck constant) [20]. The neglect of the S,-state Populations N 2 and N 3 leads to (5b)…”

Intersystem-crossing and excited-state absorption in eosin Y solutions determined by picosecond double pulse transient absorption measurements

“…From the levels 2 and 3 there occurs excitation to higher singlet states S" (level 4, excited state absorption cross-section cr ex ), radiative relaxation (level 7, spontaneous emission, radiative lifetime r rad ) and internal conversion (rate constant k k ) to the ground state (level 1), as well as intersystem-crossing to the triplet system (level 5, rate constant k hc ). The spontaneous emission may be enhanced by stimulated emission (amplified spontaneous emission [31,32]). In the triplet system the laser light causes T^T^ triplet-triplet absorption (excitation to level 6, absorption cross-section cr T ).…”

Triplet-triplet absorption of eosin Y in methanol determined by nanosecond excimer laser excitation and picosecond light continuum probing

“…(4) describes isotropic absorption with orientationally averaged absorption cross sections <x L , o cx , and <7T<L. An isotropic treatment of the absorption dynamics is appropriate, because the orientational anisotropy caused by electric dipole interaction is averaged out on a nanosecond time scale (r or <KAt L ) [58].…”

“…Amplification of spontaneous emission by stimulated emission (amplified spontaneous emission [58]) is not included in the equation system (for discussion see below). The initial conditions of the level populations are tf,(/'=-oo, z)=JV 0 and tf 3 (f'=-oo, z') = AT 5 (t' = -oo, z') =0 where N Q is the total dye number density.…”

“…The medium behaves like a fast saturable absorber with a saturation intensity of [58,59 ] AatxT is indicated by a vertical bar. The dashed curve is calculated for /CS kSo =0(^5, = 5 X10 8 s"* 1 ) and A/ L = 100 jis.…”