Rotation-free transmission measurements governed by ground-state recovery of coumarin 102, coumarin 138 and coumarin 339 dyes in ethanol solutions were performed for the first time by pump-probe technique using 35 ps pulses of Nd:YAG laser at 355 nm. Recovery of absorption is characterized by simple exponential behaviour with relaxation times of 4.0, 3.7 and 3.0 ns respectively for C 102, C 138 and C 339. These values are comparable to the lifetimes of the first excited singlet states.

Tetraphenyl silicate and related phenyl-alkyl silicates, an interesting class of compounds with applications in high vacuum technology, belong to the class of non-rigid molecules where free or restricted internal rotation of the substituent phenyl and alkyl groups provide several possible relative orientations. This may result in the formation of different phases under different conditions, providing results of fundamental interest in molecular dynamics. We have recently studied the laser Raman and infrared spectra of some of these compounds including tetraphenyl, phenyl triphenoxy, alkyl triphenyl, diphenyl dialkyl, phenyl trialkyl, and tetra alkyl silicates. Changes are observed in the spectra of these molecules with temperature, and these indicate the onset of restricted rotation at lower temperatures. These spectral changes and assignments are discussed in the paper.

A 1Σ u + -X 1Σ g + emission in Na2 is observed following excitation ofB 1π u by various lines of an argon ion laser. The excitation energy ofB 1π u is collisionally transferred to the (2)1Σ g + which then radiatively populates theA 1Σ u + state. The Na vapour is contained in a stainless steel crossed heat pipe with Ar buffer gas and temperature around 600°C. For all laser lines except 4579 Å, the coarse features ofA-X emission are independent of the laser wavelength. However, at high resolution the finer differences between different laser line excitation are explained. Variousv′-v″ transitions in this emission are identified. Computer simulation is presented to help explain some features of this emission.

Laser induced photodissociation of NaRb molecule has been observed when a mixture of Na and Rb metal vapour in a glass cell was irradiated by different lines of an argon ion laser. The photo reaction NaRb(X 1 ∑ + )+(Ar + laser photon)→ Na∗(3P)+Rb(5S) has been studied and relative cross section for various laser wavelenghts is measured. The variation of the relative photodissiciation cross section versus the laser wavelength shows a peak around 4727 Å. This quasi-resonance can be explained if we assume the photodissociation to take place in the continuum of D 1 π state. Na∗(3P), a product of photodissociation emits both the D 1 (5896 Å) and D 2 (5890 Å) lines. It is argued that D 1 π is strongly perturbed by the d 3 π state and possibly by e 3 ∑ + state.

Laser-induced photodissociation of NaCs molecule has been observed when a mixture of Na and Cs metal vapour in a glass cell was irradiated by most of the lines of an argon ion laser. The photodissociation results in the 3P state of Na atoms which is correlated with theF 1Σ+ and G1π molecular states of NaCs. Distribution of photofragments over fine structure components 32 P 3/2 and 32 P 1/2 of Na has been studied. The ratio of intensity ofD 2 line (5890 Å) toD 1 line (5896 Å) of Na varies from around 2 at 5145 Å to about 3.5 at 4579 Å. The relative photodissociation cross-section increases monotonically as the wave-length of laser light decreases from 5145 Å to 4579 Å. It is seen that the 4579 Å photon is about 200 times more effective than the 5145 Å photon in causing the photoreaction NaCs + (Ar+ photon) → Na*(3P) + Cs(6S).

Chemischer InformationsdienstVolume 12, Issue 48 Physical Inorganic Chemistry ChemInform Abstract: INTENSITY MEASUREMENT OF LASER-EXCITED FLUORESCENCE IN THE B3ΠU(0+)-X1ΣG+ SYSTEM OF DIATOMIC IODINE T. K. BALASUBRAMANIAN, T. K. BALASUBRAMANIANSearch for more papers by this authorG. L. BHALE, G. L. BHALESearch for more papers by this authorM. N. DIXIT, M. N. DIXITSearch for more papers by this authorN. A. NARASIMHAM, N. A. NARASIMHAMSearch for more papers by this author T. K. BALASUBRAMANIAN, T. K. BALASUBRAMANIANSearch for more papers by this authorG. L. BHALE, G. L. BHALESearch for more papers by this authorM. N. DIXIT, M. N. DIXITSearch for more papers by this authorN. A. NARASIMHAM, N. A. NARASIMHAMSearch for more papers by this author First published: December 1, 1981 https://doi.org/10.1002/chin.198148002AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue48December 1, 1981 RelatedInformation

Fluorescence was excited in the B3Πu(0+)-X1Σg+ system of diatomic iodine by means of the 5145-Å line of an Ar+ laser and the 6328-Å line of a HeNe laser. The resulting spectrum was recorded on a SPEX double monochromator and a quantitative measurement of the intensities was carried out. The variation of the electronic transition moment M(R) with R centroid observed by us shows a behavior similar to what has been reported earlier.

The 2-0, 1-0 and 0-0 bands of the ultraviolet system of PS have been analysed for their rotational structure. It is shown that they involve the transitionC 2 Σ -X 2 Π r (a). TheC 2 Σ state shows a significant spin doubling.

Rotational structure of emission bands of the PO molecule in the region 5300–3800 Å is analyzed. The spectrum is attributed to 5 electronic transitions A2Σ+–B2Σ+, F2Σ+–B2Σ+, G2Σ+–B2Σ+, H2Σ+–B2Σ+, and I2Σ+–B2Σ+, where F, G, H, and I are the new electronic states and A and B are the upper states of the well-known γ and β bands respectively. Practically all the new 2Σ states are found to be perturbed. A qualitative account of these perturbations together with a deperturbation of certain levels is given. A number of cases of predissociation are also observed. This predissociation is attributed to the presence of 4Πi, and A′2Σ+ states, which dissociate to the ground state atomic products. From this an upper limit of the dissociation energy of the ground state of PO is determined to be D0 = 49 536 cm−1. The A, D, E, G, H, and I states of this molecule are assigned as Rydberg states corresponding to the σ4s, π4p, δ3d, σ4p, σ3d, and σ5s orbitals, respectively. From them a value of 67 570 cm−1 is evaluated for the first ionization potential of PO. All the electronic states established for this molecule are described in terms of electron configurations.

The1Π-X 1Σ bands of AsN were excited by means of radio-frequency discharge through nitrogen and helium and traces of arsenic. The 0-0 band (2784.25 Å) and the 0-1 band (2868.74 Å) were photographed in the third order of a 6.6 meter concave grating spectrograph at a dispersion of 0.38 Å/mm. and analysed for their rotational structure. Perturbations observed in the1Π state were studied in detail.

A rotational analysis of the 0–0, 0–1, and 0–2 bands of the D–B and D′–B systems of PO in the region 5500–6900 Å has been carried out from a spectrum obtained at a resolution higher than that of previous workers (Couet and Guenebaut 1966; Couet et al. 1967). The mutual perturbation between D2Πr and D′2Πr has been confirmed from the rotational analysis of the 0–0 and 0–1 bands of the D–A and D′–X systems in the region 2000–2200 Å. The analysis of the D′–X bands has shown that the previously reported E′ state lying between the D and D′ states is actually part of the D′ state. The constants of the D2Πr, D′ 2Πr, B2Σ+, and X2Π states are evaluated and compared with the constants of earlier workers to remove the inconsistency existing in their values for the B and X states.The isotopic bands corresponding to P18O of the D–B and D′–B systems are obtained, thus showing that the D′ state has an anomalous isotopic shift and that the observed levels of the D and D′ states have the vibrational quantum number ν =.

The spectra of P16O and P18O were excited in sealed discharge tubes containing neon (2–3 mm. pressure), oxygen gas enriched to 65 per cent. of18O and trace amounts of phosphorus vapour and photographed on a 3 m. grating spectrograph at a dispersion of 2·5 Å/mm. Isotope shift studies in theβ-bands confirmed the earlier vibrational scheme of Curryet al. and showed conclusively that the red as well as the violet degraded bands belonged to the sameβ-system. The present studies of isotope shifts also confirmed the vibrational assignments of the extensive ultraviolet bands involving the2 Σ −−X2 Π transition and theγ-bands (A2 Σ +−X2 Π). In the case of the visible bands, they provided evidence for the first time that the bands at 5585 Å, 5962 Å and 6385 Å belonged to one system and involved 0–0, 0–1 and 0–2 transitions respectively.

Ten ultraviolet bands of the C1 Σ u + -X1 Σ g + system of P2 involving lowv′ andv″ values have been photographed at dispersion of 0·38 and 0·56 Å/mm. and analysed for their rotational structure. While four of these bands were analysed earlier, six of them,viz., 0–10, 1–12, 2–7, 2–14, 4–8 and 6–9 have been analysed for the first time during the present studies. The rotational constants, B v S with lowv″ quantum numbers are obtained from which value of B θ ″ has been derived. The value of B θ ″ is found to be in agreement with the value obtained by Douglas and Rao from their study of A1 Π g-X1 Σ g + bands of P2.