Katsumi Sakurai

Spectral Study of NO2 Fluorescence Excited by 11 Lines of Argon and Krypton Ion Lasers

High‐resolution spectra of the fluorescence of NO2 excited by 11 Ar+ and Kr+ laser lines between 4579 and 5208 A, have been obtained at NO2 pressures from 10−3–10 torr. Rotational lines as well as vibrational bands are observed superimposed on a continuum extending from the exciting line to the observation limit of 7500 A. Vibrational assignments of the fluorescent bands have been made, and vibrational constants of the gound electronic state have been determined. The pressure dependence of absorption coefficients of NO2 at the laser wavelengths also was measured; an excited‐state lifetime near 10−5 sec was estimated from these absorption coefficients. In addition, the lifetime of excited NO2 was measured to be 5 × 1015 sec from the observation of the increase in visual size of the fluorescence beam at low pressure. Preliminary values of σ2τ (square of collision diameter times lifetime) of the fluorescence excited by the 4880‐A line were measured to be approximately 7 × 10−20 cm2·sec for line emission and ...

Laser‐Induced Fluorescence of BaO

Fluorescence spectra of the A 1Σ − X 1Σ system of BaO excited by seven visible Ar ion laser lines have been observed over a wavelength region from the exciting lines to beyond 1000 nm. The strongest fluorescence was observed from υ′ = 8, J′ = 49 excited by 488.0 nm and υ′ = 7, J′ = 3 and 7 excited by 496.5 nm. The rotational and vibrational assignments of the various excitation transitions have been made, and rotational and vibrational constants for the lower electronic state were obtained. A rotational perturbation in υ′ = 7 of the upper electronic state was found. Studies have been made, from 0.4 to 40 torr, of the collisional energy transfer to other rotational and vibrational levels of the A 1Σ state after optical pumping by laser lines. The lifetime of the A 1Σ state of BaO was found to be 12 ± 3 × 10−6 sec. The BaO molecules were produced by gas‐phase chemical reactions between O2 and Ba vapor in an inert gas at room temperature. A weak chemiluminescence of the A 1Σ − X 1Σ system of BaO was observed.

LASER PHOTOLUMINESCENCE OF CALCIUM MOLECULES

Calcium diatomic molecules were produced in a heat‐pipe oven at temperatures from 1000 to 1200 K. Photoluminescence of Ca2 has been studied with various laser sources and with white light. Discrete, sharp line spectra are attributed to known bound states of Ca2. A broad continuum emission with an oscillatory intensity distribution is associated with emission to the repulsive part of the lower state. A weak continuum emission to another repulsive state also has been observed. The observed strong emission from the atomic resonance lines at 422.7 and 657.3 nm probably is caused by dissociation of excited Ca2 molecules. The laser‐excited photoluminescence experiments suggest that the ground state of Ca2 is repulsive and that the lowest observed bound state of Ca2 correlates with the 3P atomic state.

Measurements of Lifetimes and Quenching Cross Sections of the B 3Π0u+ State of Iodine Using a Tunable Dye Laser

Lifetimes and self‐quenching cross sections of selected vibrational levels from υ′ = 0–25 of the B3Π0u+ state of I2 were measured from the direct decay of fluorescence excited by a pulsed, tunable dye laser. Large variations with υ′ of lifetimes and quenching cross sections were observed. Lifetimes changed by a factor of 3; for υ′ = 10 to 13, lifetimes were 1.5 μsec while for υ′ = 4 the lifetime was 0.53 μsec. This υ′ dependence is much larger than the calculated dependence of radiative lifetimes but can be explained by spontaneous predissociation through dissociative states crossing the B state. Smaller quenching cross sections were observed for the vibrational levels with longer lifetimes.

Lifetimes and Self‐Quenching Cross Sections of Vibrational Levels in the B State of Bromine Excited by a Tunable Dye Laser

A tunable dye laser was used to excite selected vibrational levels between υ′ = 1 and 31 of the B 3Π0u+ state of Br2. Lifetimes and self‐quenching cross sections were measured by observing the direct decay of fluorescence as a function of pressure. Large variations of lifetimes and cross sections were found; the lifetimes varied by a factor of 8, ranging from greater than 1.2 μsec near υ′ = 27 to less than 0.15 μsec near υ′ = 14. Two minima of lifetimes near υ′ = 1 and 14 can be explained by decay of the B state by means of spontaneous predissociation through dissociative states.

Laser photoluminescence of Bi2

Bismuth diatomic molecules are produced in an inert gas flow system and in a heat‐pipe oven at pressures from 10−4 to 10 torr. Photoluminescence of Bi2 has been studied with various laser sources and with white light. Strong photoluminescence is due to different vibrational–rotational transitions of the A–X system. Observed weaker photoluminescence series are due to vibrational–rotational transitions of four previously unknown electronic systems of Bi2 with ωe= 154.29±0.45 cm−1; ωe=141.23±0.35 cm−1; ωe=127.05±0.1 cm−1 and ωe=105.68±0.25 cm−1. Long v″ progressions extending over the whole Franck–Condon distribution (including both maxima) are measured for several electronic transitions. Molecular constants for the lower electronic states involved are obtained from spectroscopic analysis. The laser‐excited photoluminescence experiments suggest that A is not the first excited state in Bi2 and that X is not the ground state of Bi2 but that the X ′ state is probably the lowest energy state. Photoluminescence w...

Laser Induced Fluorescence of ClO2

Fluorescence spectra of the A(2A2)–X(2B1) system of ClO2 excited by five visible Ar‐ion laser lines (4579–4880 A) have been observed over a wavelength region from near excitation to beyond 7000 A. Approximately 60 fluorescence bands have been observed for each laser line excitation and about half of these bands have been assigned. Vibrational constants of the ground state have been calculated from observed band positions.

Lifetime measurement of a single rotational transition of the B3∏+u → X1Σg transition of iodine☆

Abstract Lifetimes, self-quenching, and vibrational and rotational energy transfer cross sections of individual rotational levels in the B 3 ∏ + u state of I 2 were measured by observing the correlation between fluorescence photons and the pulsed excitation from 514.5 and 501.7 nm argon ion lasers. Lifetimes were measured with both vibrationally resolved (1.0nm) and rotationally resolved detection (0.015 nm). The cross sections from Stern—Volmer plots were respectively, 76 and 89 A 2 with 5% accuracy for single (43-2) band emission and the P(16) line emission in the same band. The difference in cross sections is interpreted as vibrational and rotational energy transfer from the originally excited level. Measured radiative lifetimes are consistent with previous measurements except that a 10% shorter lifetime was observed with single rotational line detection.

Chemically reacting bismuth and nitrous oxide in a heat pipe oven

Abstract The chemical reactions between bismuth and oxidants in a heat pipe oven are described. Strong chemiluminescence (A2Π 1 2 → X2Π 1 2 ) was observed in the reaction with N2O and the vibrational temperature of the A2Π 1 2 state was measured to be 3150 ± 300 K.

Chemiluminescence of CaH and AIH in the reaction of the metal atoms and formaldehyde

Abstract Chemiluminescence from the reaction of calcium and aluminum with various hydrogen containing compounds in a flowing gas system and in a heat pipe oven are described. Red chemiluminescence of CaH was observed in the reaction of calcium, and weak chemiluminescence of AlH was seen in the reaction of aluminum with formaldehyde (H 2 CO). It is proposed that a reaction between metal atoms and formaldehyde may be used as a source of diatomic metallic hydrides.