The reader is provided with information about methods of calibration of light sources and photodetectors as well as responsiveness of spectral instruments ranging from near infrared to vacuum UV ...spectral, 1200 - 100 nm, and radiation intensities of up to several quanta per second in absolute and arbitrary units. The author describes for the first time original methods of measurements they created and draws upon over 40 years of experience in working with light sources and detectors to provide accurate and precise measurements. This book is the first to cover these aspects of radiometry and is divided into seven chapters that examine information about terminology, units, light sources and detectors, methods, including author's original ones, of absolute calibration of detectors, spectral instruments responsiveness, absolute measurements of radiation intensity of photoprocesses, and original methods of their study. Of interest to researchers measuring, luminescence spectra, light intensities from IR to vacuum UV, spectral range in wide-light intensity ranges, calibrate light sources and detectors, absolute or relative quantum yields of photoprocess determination.
Display omitted
•Luminescence of the HeICl ion-pairs state van der Waals complexes being HenICl cluster predissociation products have been observed and the spectra have been measured.
The letter ...presents the results of studies of population and decay of the {2,0}He2ICl(β1,vβ = 0) and {1,1}He2ICl(β1,vβ = 0) clusters. Action, pump–probe and luminescence excitation spectra as well as luminescence spectra themselves have been measured. The T-shaped HeICl(E,vE = 0 andD′,vD′ = 0) complex luminescence has been observed when the {2,0}He2ICl(β1,vβ = 0) cluster is populated. It has been shown that a population of the {1,1}He2ICl(A,13,nA) cluster at the energy higher than its dissociation threshold is accompanied by the T-shaped HeICl(A,13,nA) formation.
Display omitted
•The NeI2(E,vE,nE) luminescence has been observed under optical population of the NeI2(E,vE,nE) vdW complexes for the first time.•Lifetime of the NeI2(E,vE,nE) complex depends on the ...vE value.•Lifetime of the NeI2(E,vE = 0,nE) complex is rather large, ≈ 8 ns.
The T-shaped NeI2(E0g+) van der Waals (vdW) complexes populated in the NeI2(E,vE = 0–2, nE=0–2 ← B,19,nB = 0 ← X,0,nX = 0) excitation pathway have been studied. Analysis of the luminescence excitation spectra, luminescence spectra themselves and temporal behaviors of the luminescence intensities of the transitions observed has been carried out. The NeI2(E,vE,nE) luminescence has been discovered. This is the first direct observation of a halogen molecule vdW complex luminescence. It has also been found that lifetime of the NeI2(E,vE,nE) complex depends on the vE value: it is equal to 8 ns for the NeI2(E,vE = 0,nE) when vibrational predissociation (VP) is impossible and ≤2 ns when VP channels are open.
Display omitted
•The N2I2(E0+g) van der Waals complexes have been studied for the first time.•Potential parameters of the N2I2(E;vE = 0,3;nE) complexes have been determined.•Binding energies of the ...N2I2(X0+g and B0+u,vB = 19) complexes have been estimated.•Ab initio calculation for the N2I2(X) complex have been performed.
The N2I2(E0g+) van der Waals complexes have been observed and studied for the first time. Analysis of the luminescence excitation spectra as well as luminescence spectra themselves in the spectral ranges, where the I2(D0u+ → X0g+, β1g → A1u and D’2g → A’2u) transitions can occur, has been carried out. Branching ratios of the iodine molecule state formation and vibronic level population have been determined. Ab initio calculations of the N2I2(X0g+) complex ground state at complete basis set limit are performed. It is shown that it has two stable, parallel and linear, isomers separated by an energy barrier. The parallel isomer is observed in our experiments. Binding energies of the N2I2(X0g+,vX = 0,nX = 0, B0u+,vB = 19,nB = 0) as well as the some spectroscopic parameters of the N2I2(E,vE = 0, 3) complexes have been also estimated.
Display omitted
•The ArI2(E0g+) van der Waals complexes have been observed and studied for the first time.•Luminescence spectra of the complex predissociation products have been measured.•The ...dominant decay channel of ArI2(E) complexes is electronic predissociation.•Spectroscopic parameters of the ArI2(E) state have been determined.
The ArI2(E0g+) van der Waals complexes have been observed and studied for the first time. Analysis of the luminescence excitation spectra as well as luminescence spectra themselves in the spectral ranges, where the I2(E0g+→B0u+,D0u+→X0g+,β1g→A1u and D′2g→A′2u) transitions can occur, has been carried out. It has been shown that the I2(D→X, β→A and D′→A′) luminescence is due to ArI2(E←B) transitions with subsequent predissociation. We have determined the spectroscopic parameters of the ArI2(E,νE=0–3) complexes.
It has been shown that rate of vibrational predissociation is ∼10 times less than total rate of the ArI2(E,νE=0–3)→Ar+I2(D, β, D′) electronic predissociation.
Display omitted
•The HeI2(E0g+) van der Waals complexes have been observed and studied.•Luminescence spectra of the complex predissociation products have been measured.•Dissociation energy of the ...HeI2(E) state have been determined.
The T-shaped HeI2(E0g+) van der Waals complexes populated in the HeI2(E,vE=0–2,nE=0←B,19,nB=0←X,0,nX) excitation pathway have been studied. Analysis of the luminescence excitation spectra as well as the I2(E0g+→B0u+, D0u+→X0g+, and D′2g→A′2u) luminescence spectra themselves has been carried out. It has been shown that the I2(D→X, and D′→A′) luminescence is due to HeI2(E←B) transitions with subsequent electronic predissociation. We have determined dissociation energies of the HeI2(E,vE=0–2) complexes, vibrational populations of the E, D states and branching ratios of vibrational and electronic predissociations. One can suppose that luminescence of the HeI2(E,vE=0,nE=0) complexes occurs.
Display omitted
•Collision-induced non-adiabatic transitions from I2 ion-pair states are studied.•It allows to understand how symmetry of electronic states affects these processes.•It is shown that ...the I2 lasing does not occur due to collision-induced transitions.
Non-adiabatic transitions from the I2(E0g+, D0u+, β1g and D′2g) states to first tier ion-pair (IP) states induced by collisions with Ar atoms have been investigated. The stepwise laser excitation schemes have been used for selective population of close-lying vibronic states: E, vE=13, D, vD=18, β, vβ=19 and D′2g, vD′=23. Rate constants of population of the first tier ion-pair states from the optically populated rovibronic states as well as rate constants of depopulation of the states have been determined. Analysis of the mechanism of the transitions has been carried out.
We find that the λlummax≈3410Å luminescence band in the case of optical population of the D and β states cannot be described assuming the collision-induced non-adiabatic transitions only. We conclude that there is an additional radiative channel for population of the states, probably, due to the formation of the ArI2(IP) van der Waals complexes.
The article presents the analysis of the ArICl(IP,v
IP
,n
IP
) population and decay at energies lower than the ArICl(E,v
E
= 0,n
E
) dissociation limit (IP = E0
+
,
, β1), v
IP
= 0, 1, n
IP
are ...quantum numbers of the van der Waals (vdW) modes). It shows that the ArICl(IP,v
IP
,n
IP
) lifetimes determined at spectral ranges where the ArICl(E→X,
, and β→A) luminescence takes place, are the same, τ = 20.3 ± 1.0 ns, i.e. strongly mixed complex states are populated in the ArICl(IP,v
IP
,n
IP
← A,v
A
,n
A
) transitions, and principal channel of the complex decay is emission. We have estimated the ArICl(E0
+
,v
E
= 0) binding energy and studied the ArICl(IP,v
IP
,n
IP
) population and decay at energies higher than the ArICl(E,v
E
= 0,n
E
) dissociation limit. Our research shows that the ArICl(IP,v
IP
,n
IP
) wave functions corresponding to specific n
IP
vdW mode depend on the mode, but they are approximately constant in some spectral ranges. The ArICl(IP,v
IP
,n
IP
) complex decays to free ICl(E0
+
,v
E
,
and β1,v
β
) molecules. We have determined the probabilities of these decay channels and shown that all the ICl(IP) states are mixed under the action of the Ar atom, i.e. this atom does not behave in the ArICl(IP,v
IP
,n
IP
) complexes as a 'spectator' as it occurs in the RgI
2
(IP) states.
The article presents results of experimental and theoretical analysis of the T‐shaped and linear HeICl van der Waals complexes in the valence A1 and ion‐pair β1 states as well as the ...HeICl(A1,vA,nA←X0+,vX=0,nx and β1,vβ,nβ←A1,vA,nA) optical transitions (ni are quantum numbers of the vdW) modes). The HeICl(β1,vβ,nβ)→He+ICl(E0+,
D'2
${{D}^{{ {\prime}}}2}$
, β1) decay are also studied. Luminescence spectra of the HeICl(β1,vβ=0–3,nβ) complex electronic (ICl(E0+,vE,
D'2,vD'
${{D}^{{ {\prime}}}2,{v}_{{D}^{{ {\prime}}}$
) and vibrational ICl(β1,vβ) predissociation products are measured, and branching ratios of decay channels are determined. To construct potential energy surfaces for the HeICl(A1, β1) states, we utilized the intermolecular diatomic‐in‐molecule perturbation theory first order method. Experimental and calculated spectroscopic characteristics of the A1 and β1 states agree well. Comparison of the experimental and calculated pump‐probe, action and excitation spectra shows that the calculated spectra describe the experimental spectra adequately.
Experimental and calculated spectroscopic characteristics of the HeICl valence, A1, and ion‐pair, β1, van der Waals complexes agree well. A comparison of the experimental and calculated pump‐probe, action and excitation spectra shows that the calculated spectra describe the experimental spectra adequately.
PDF
